| Members | Union1 |
|---|
| 2,731,419 | National Education Association of the United States2 |
| 1,505,100 | Service Employees International Union3 |
| 1,459,511 | American Federation of State, County, and Municipal Employees |
| 1,396,174 | International Brotherhood of Teamsters3 |
| 1,311,548 | United Food and Commercial Workers International Union |
| 828,512 | American Federation of Teachers |
| 754,978 | United Steelworkers of America |
| 704,794 | International Brotherhood of Electrical Workers |
| 669,772 | Laborers' International Union of North America |
| 653,781 | International Association of Machinists and Aerospace Workers |
| 557,099 | International Union, United Automobile, Aerospace, and Agricultural Implement Workers of America |
| 545,638 | Communications Workers of America |
| 522,416 | United Brotherhood of Carpenters and Joiners of America2 |
| 455,346 | Union of Needletrades, Industrial, and Textile Employees |
| 424,579 | Longshore and Warehouse Union |
| 392,584 | International Union of Operating Engineers |
| 361,362 | Maritime Trades |
| 324,043 | United Association of Journeymen and Apprentices of the Plumbing and Pipe-Fitting Industry of the U.S. and Canada |
| 292,221 | National Association of Letter Carriers |
| 286,700 | American Postal Workers Union |
| 271,463 | International Association of Fire Fighters |
| 269,204 | National Postal Mail Handlers Union |
| 245,011 | Paper, Allied-Industrial, and Chemical International Union |
| 226,975 | American Federation of Government Employees |
| 180,598 | Amalgamated Transit Union |
| 152,294 | American Nurses Association2 |
| 148,806 | Sheet Metal Workers International Association |
| 127,278 | International Brotherhood of Painters and Allied Trades |
| 125,437 | International Association of Bridge, Structural, Ornamental, and Reinforcing Iron Workers |
| 125,398 | Transport Workers Union of America |
| 125,000 | Building and Construction Trades |
| 111,851 | American Association of Classified School Employees2 |
| 105,460 | The National Rural Letter Carriers' Association2 |
1. Unless otherwise noted, unions are AFL-CIO affiliated.
2. Not AFL-CIO affiliated.
3. Severed ties with the AFL-CIO in July 2005.
