Massachusetts held special elections on November 3, 2015, deciding 1 legislative seat.
Legislature
- House (160 seats): 125 D, 35 R before the election, 125 D, 35 R after; control stayed with Democrats.
- Senate (40 seats): 34 D, 6 R before the election, 33 D, 5 R, 2 other or vacant after; control stayed with Democrats.
Legislative races
| Race | Winner | Others | Notes |
|---|---|---|---|
| Senate 2nd Plymouth and Bristol | Michael D. Brady (D) 56.9% | Geoff Diehl (R) 40.5%, Anna Grace Raduc (I) 2.6% |