They are bus and shuttle drivers who work at the Massachusetts Institute of Technology and the Cambridge Health Alliance, which serves three hospitals.
They voted Thursday by more than a 2-1 margin to join Teamster Local 25. The vote was 19-8.
The drivers join their colleagues—270 attendants, cashiers and valet workers at Standard—who voted to join Local 25 in October.
The workers want job security, respect and fair pay.
Last February, 334 workers at Central Parking in the Boston area joined Local 25.