diff --git a/src/lib/http.ts b/src/lib/http.ts
index 0bd9077..e70369b 100644
--- a/src/lib/http.ts
+++ b/src/lib/http.ts
@@ -205,6 +205,31 @@ export class HttpClient {
     return Buffer.from(await response.arrayBuffer());
   }
 
+  async adoUpload<T>(
+    path: string,
+    buffer: Buffer,
+    contentType: string,
+    opts: { timeoutMs?: number } = {}
+  ): Promise<T> {
+    const baseUrl = this.config.ado.baseUrl;
+    if (!baseUrl) throw new PncliError('Azure DevOps baseUrl not configured. Run: pncli config init');
+
+    const url = buildUrl(baseUrl, path);
+
+    if (this.dryRun) {
+      fs.writeSync(process.stderr.fd, `DRY RUN: POST ${url}\nBody: <binary ${buffer.length} bytes>\n`);
+      process.exitCode = ExitCode.SUCCESS;
+      throw new PncliError('dry-run', 0);
+    }
+
+    const fetcher = await this.getAdoFetcher();
+    return request<T>(url, {
+      method: 'POST',
+      headers: { 'Accept': 'application/json', 'Content-Type': contentType },
+      body: buffer
+    }, opts.timeoutMs ?? 60000, fetcher);
+  }
+
   async adoBuffer(absoluteUrl: string, opts: { timeoutMs?: number } = {}): Promise<Buffer> {
     if (this.dryRun) {
       fs.writeSync(process.stderr.fd, `DRY RUN: GET ${absoluteUrl}\n`);
diff --git a/src/lib/mime.test.ts b/src/lib/mime.test.ts
new file mode 100644
index 0000000..1ffbf2b
--- /dev/null
+++ b/src/lib/mime.test.ts
@@ -0,0 +1,64 @@
+import { describe, it, expect } from 'vitest';
+import { guessMimeType } from './mime.js';
+
+describe('guessMimeType', () => {
+  it('returns correct MIME type for image extensions', () => {
+    expect(guessMimeType('photo.jpg')).toBe('image/jpeg');
+    expect(guessMimeType('photo.jpeg')).toBe('image/jpeg');
+    expect(guessMimeType('icon.png')).toBe('image/png');
+    expect(guessMimeType('animation.gif')).toBe('image/gif');
+    expect(guessMimeType('logo.svg')).toBe('image/svg+xml');
+  });
+
+  it('returns correct MIME type for document extensions', () => {
+    expect(guessMimeType('document.pdf')).toBe('application/pdf');
+    expect(guessMimeType('notes.txt')).toBe('text/plain');
+    expect(guessMimeType('app.log')).toBe('text/plain');
+    expect(guessMimeType('data.csv')).toBe('text/csv');
+    expect(guessMimeType('config.json')).toBe('application/json');
+    expect(guessMimeType('data.xml')).toBe('application/xml');
+    expect(guessMimeType('readme.md')).toBe('text/markdown');
+    expect(guessMimeType('page.html')).toBe('text/html');
+    expect(guessMimeType('page.htm')).toBe('text/html');
+  });
+
+  it('returns correct MIME type for Microsoft Office extensions', () => {
+    expect(guessMimeType('report.doc')).toBe('application/msword');
+    expect(guessMimeType('report.docx')).toBe('application/vnd.openxmlformats-officedocument.wordprocessingml.document');
+    expect(guessMimeType('spreadsheet.xls')).toBe('application/vnd.ms-excel');
+    expect(guessMimeType('spreadsheet.xlsx')).toBe('application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
+  });
+
+  it('returns correct MIME type for archive extensions', () => {
+    expect(guessMimeType('archive.zip')).toBe('application/zip');
+    expect(guessMimeType('archive.tar')).toBe('application/x-tar');
+    expect(guessMimeType('archive.gz')).toBe('application/gzip');
+  });
+
+  it('is case-insensitive', () => {
+    expect(guessMimeType('PHOTO.JPG')).toBe('image/jpeg');
+    expect(guessMimeType('Photo.PNG')).toBe('image/png');
+    expect(guessMimeType('Document.PDF')).toBe('application/pdf');
+  });
+
+  it('works with absolute paths', () => {
+    expect(guessMimeType('/home/user/documents/report.pdf')).toBe('application/pdf');
+    expect(guessMimeType('/var/log/app.log')).toBe('text/plain');
+  });
+
+  it('works with relative paths', () => {
+    expect(guessMimeType('./photos/vacation.jpg')).toBe('image/jpeg');
+    expect(guessMimeType('../../docs/readme.md')).toBe('text/markdown');
+  });
+
+  it('returns application/octet-stream for unknown extensions', () => {
+    expect(guessMimeType('file.unknown')).toBe('application/octet-stream');
+    expect(guessMimeType('file.xyz')).toBe('application/octet-stream');
+    expect(guessMimeType('file.custom')).toBe('application/octet-stream');
+  });
+
+  it('returns application/octet-stream for files without extensions', () => {
+    expect(guessMimeType('Makefile')).toBe('application/octet-stream');
+    expect(guessMimeType('README')).toBe('application/octet-stream');
+  });
+});
diff --git a/src/lib/mime.ts b/src/lib/mime.ts
new file mode 100644
index 0000000..cf96806
--- /dev/null
+++ b/src/lib/mime.ts
@@ -0,0 +1,36 @@
+import { extname } from 'path';
+
+/**
+ * Guess MIME type from file extension.
+ * Falls back to application/octet-stream for unknown extensions.
+ *
+ * @param filePath - Path to the file (can be absolute or relative)
+ * @returns MIME type string
+ */
+export function guessMimeType(filePath: string): string {
+  const ext = extname(filePath).toLowerCase();
+  const map: Record<string, string> = {
+    '.jpg': 'image/jpeg',
+    '.jpeg': 'image/jpeg',
+    '.png': 'image/png',
+    '.gif': 'image/gif',
+    '.svg': 'image/svg+xml',
+    '.pdf': 'application/pdf',
+    '.txt': 'text/plain',
+    '.log': 'text/plain',
+    '.csv': 'text/csv',
+    '.json': 'application/json',
+    '.xml': 'application/xml',
+    '.zip': 'application/zip',
+    '.tar': 'application/x-tar',
+    '.gz': 'application/gzip',
+    '.md': 'text/markdown',
+    '.html': 'text/html',
+    '.htm': 'text/html',
+    '.doc': 'application/msword',
+    '.docx': 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+    '.xls': 'application/vnd.ms-excel',
+    '.xlsx': 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
+  };
+  return map[ext] ?? 'application/octet-stream';
+}
diff --git a/src/services/ado/client/work.test.ts b/src/services/ado/client/work.test.ts
index 04d0a53..57ea78c 100644
--- a/src/services/ado/client/work.test.ts
+++ b/src/services/ado/client/work.test.ts
@@ -1,3 +1,6 @@
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
 import { describe, it, expect, vi, afterEach } from 'vitest';
 import { AdoWorkClient } from './work.js';
 import { HttpClient } from '../../../lib/http.js';
@@ -303,3 +306,85 @@ describe('AdoWorkClient — downloadAttachment', () => {
     expect(buffer[0]).toBe(137);
   });
 });
+
+describe('AdoWorkClient — uploadAttachment', () => {
+  afterEach(() => { vi.unstubAllGlobals(); });
+
+  it('uploads the file and links it to the work item', async () => {
+    const tmpFile = path.join(os.tmpdir(), 'pncli-test-report.txt');
+    fs.writeFileSync(tmpFile, 'file content');
+
+    const capturedRequests: Array<{ url: string; method: string; body: unknown; contentType?: string }> = [];
+    const attachmentResponse = {
+      id: 'att-guid-123',
+      url: 'https://ado.example.com/myorg/_apis/wit/attachments/att-guid-123',
+      name: 'pncli-test-report.txt'
+    };
+
+    vi.stubGlobal('fetch', async (url: string, init: RequestInit) => {
+      const contentType = (init.headers as Record<string, string>)['Content-Type'] ?? '';
+      let body: unknown = undefined;
+      if (typeof init.body === 'string') {
+        body = JSON.parse(init.body);
+      }
+      capturedRequests.push({ url: String(url), method: String(init.method), body, contentType });
+
+      if (String(url).includes('attachments?fileName')) {
+        return new Response(JSON.stringify(attachmentResponse), { status: 200 });
+      }
+      return new Response(JSON.stringify(makeWorkItem('')), { status: 200 });
+    });
+
+    const http = new HttpClient(makeConfig());
+    const client = new AdoWorkClient(http);
+    const result = await client.uploadAttachment('myorg', 42, tmpFile);
+
+    fs.unlinkSync(tmpFile);
+
+    expect(result.id).toBe('att-guid-123');
+    expect(result.url).toBe('https://ado.example.com/myorg/_apis/wit/attachments/att-guid-123');
+
+    // First request: upload to attachments endpoint
+    expect(capturedRequests[0].url).toContain('_apis/wit/attachments');
+    expect(capturedRequests[0].url).toContain('fileName=pncli-test-report.txt');
+    expect(capturedRequests[0].method).toBe('POST');
+    expect(capturedRequests[0].contentType).toBe('text/plain');
+
+    // Second request: PATCH work item to link the attachment
+    expect(capturedRequests[1].url).toContain('_apis/wit/workitems/42');
+    expect(capturedRequests[1].method).toBe('PATCH');
+    const patch = capturedRequests[1].body as Array<{ op: string; path: string; value: { rel: string; url: string } }>;
+    expect(patch[0].op).toBe('add');
+    expect(patch[0].path).toBe('/relations/-');
+    expect(patch[0].value.rel).toBe('AttachedFile');
+    expect(patch[0].value.url).toBe(attachmentResponse.url);
+  });
+
+  it('includes comment in the relation attributes when provided', async () => {
+    const tmpFile = path.join(os.tmpdir(), 'pncli-test-notes.txt');
+    fs.writeFileSync(tmpFile, 'meeting notes');
+
+    const capturedBodies: unknown[] = [];
+
+    vi.stubGlobal('fetch', async (url: string, init: RequestInit) => {
+      if (String(url).includes('attachments?fileName')) {
+        return new Response(JSON.stringify({
+          id: 'att-guid-456',
+          url: 'https://ado.example.com/myorg/_apis/wit/attachments/att-guid-456',
+          name: 'pncli-test-notes.txt'
+        }), { status: 200 });
+      }
+      capturedBodies.push(JSON.parse(init.body as string));
+      return new Response(JSON.stringify(makeWorkItem('')), { status: 200 });
+    });
+
+    const http = new HttpClient(makeConfig());
+    const client = new AdoWorkClient(http);
+    await client.uploadAttachment('myorg', 42, tmpFile, 'Meeting notes');
+
+    fs.unlinkSync(tmpFile);
+
+    const patch = capturedBodies[0] as Array<{ op: string; path: string; value: { rel: string; attributes?: { comment: string } } }>;
+    expect(patch[0].value.attributes?.comment).toBe('Meeting notes');
+  });
+});
diff --git a/src/services/ado/client/work.ts b/src/services/ado/client/work.ts
index ab7d26d..d4bd36a 100644
--- a/src/services/ado/client/work.ts
+++ b/src/services/ado/client/work.ts
@@ -1,4 +1,7 @@
+import { readFileSync } from 'fs';
+import { basename } from 'path';
 import type { HttpClient } from '../../../lib/http.js';
+import { guessMimeType } from '../../../lib/mime.js';
 import type {
   AdoWorkItem,
   AdoWorkItemComment,
@@ -140,4 +143,35 @@ export class AdoWorkClient {
   async downloadAttachment(absoluteUrl: string): Promise<Buffer> {
     return this.http.adoBuffer(absoluteUrl);
   }
+
+  async uploadAttachment(
+    collection: string,
+    workItemId: number,
+    filePath: string,
+    comment?: string
+  ): Promise<AdoWorkItemAttachment> {
+    const fileContent = readFileSync(filePath);
+    const fileName = basename(filePath);
+    const mimeType = guessMimeType(filePath);
+
+    // Step 1: Upload the file to ADO's attachment store
+    const attachment = await this.http.adoUpload<AdoWorkItemAttachment>(
+      `/${encodeURIComponent(collection)}/_apis/wit/attachments?fileName=${encodeURIComponent(fileName)}&api-version=${API}`,
+      fileContent,
+      mimeType
+    );
+
+    // Step 2: Link the uploaded attachment to the work item
+    const relationValue: Record<string, unknown> = {
+      rel: 'AttachedFile',
+      url: attachment.url,
+      ...(comment ? { attributes: { comment } } : {})
+    };
+    await this.http.ado<AdoWorkItem>(
+      `/${encodeURIComponent(collection)}/_apis/wit/workitems/${workItemId}?api-version=${API}`,
+      { method: 'PATCH', body: [{ op: 'add', path: '/relations/-', value: relationValue }], headers: { 'Content-Type': 'application/json-patch+json' } }
+    );
+
+    return attachment;
+  }
 }
diff --git a/src/services/ado/commands/work.ts b/src/services/ado/commands/work.ts
index 0141d96..af3a2ba 100644
--- a/src/services/ado/commands/work.ts
+++ b/src/services/ado/commands/work.ts
@@ -247,6 +247,21 @@ export function registerAdoWorkCommands(ado: Command): void {
       } catch (err) { fail(err, 'ado', 'work-list-attachments', start); }
     });
 
+  work
+    .command('add-attachment')
+    .description('Upload a local file and attach it to a work item')
+    .requiredOption('--id <n>', 'Work item ID')
+    .requiredOption('--file <path>', 'Path to the file to upload')
+    .option('--comment <text>', 'Optional comment for the attachment')
+    .action(async (opts: { id: string; file: string; comment?: string }) => {
+      const start = Date.now();
+      try {
+        const { collection, workClient } = getAdoContext(ado);
+        const data = await workClient.uploadAttachment(collection, parseInt(opts.id, 10), opts.file, opts.comment);
+        success(data, 'ado', 'work-add-attachment', start);
+      } catch (err) { fail(err, 'ado', 'work-add-attachment', start); }
+    });
+
   work
     .command('download-attachment')
     .description('Download a work item attachment to .pncli/ (or --dir)')
diff --git a/src/services/jira/client.ts b/src/services/jira/client.ts
index f405e28..a34d59b 100644
--- a/src/services/jira/client.ts
+++ b/src/services/jira/client.ts
@@ -1,6 +1,7 @@
 import { readFileSync } from 'fs';
-import { basename, extname } from 'path';
+import { basename } from 'path';
 import type { HttpClient } from '../../lib/http.js';
+import { guessMimeType } from '../../lib/mime.js';
 import type {
   JiraIssue,
   JiraTransition,
@@ -292,35 +293,6 @@ export class JiraClient {
   }
 }
 
-/** Guess MIME type from file extension; falls back to application/octet-stream. */
-function guessMimeType(filePath: string): string {
-  const ext = extname(filePath).toLowerCase();
-  const map: Record<string, string> = {
-    '.jpg': 'image/jpeg',
-    '.jpeg': 'image/jpeg',
-    '.png': 'image/png',
-    '.gif': 'image/gif',
-    '.svg': 'image/svg+xml',
-    '.pdf': 'application/pdf',
-    '.txt': 'text/plain',
-    '.log': 'text/plain',
-    '.csv': 'text/csv',
-    '.json': 'application/json',
-    '.xml': 'application/xml',
-    '.zip': 'application/zip',
-    '.tar': 'application/x-tar',
-    '.gz': 'application/gzip',
-    '.md': 'text/markdown',
-    '.html': 'text/html',
-    '.htm': 'text/html',
-    '.doc': 'application/msword',
-    '.docx': 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
-    '.xls': 'application/vnd.ms-excel',
-    '.xlsx': 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
-  };
-  return map[ext] ?? 'application/octet-stream';
-}
-
 /** Map a Jira field schema to the recommended pncli CustomFieldType. */
 function schemaToPncliType(schema?: { type: string; custom?: string }): CustomFieldType | undefined {
   if (!schema) return undefined;