While the profession of social work and the labor movement have moved in different directions since the post-WW2 era, recent events, such as the dominance of managed care and cuts in government financing, have led social workers to rediscover unions as potential political and workplace allies. This essay uses interviews, union documents and secondary data to document both historical and contemporary alliances between unions and social workers. Specifically, the cases of public sector workers organized through Service Employees International Union 535 and the affiliation of the Clinical Social Work Federation with the Office and Professional Employees International Union are examined and compared. Implications for community and workplace organizing are developed.