Massachusetts held special elections on November 7, 2017, deciding 2 legislative seats.
Legislature
- House (160 seats): 125 D, 35 R before the election, 117 D, 34 R, 9 other or vacant after; control stayed with Democrats.
- Senate (40 seats): 34 D, 6 R before the election, 34 D, 6 R after; control stayed with Democrats.
Legislative races
| Race | Winner | Others | Notes |
|---|---|---|---|
| House 1st Berkshire | John Barrett (D) 73.4% | Christine M. Canning (R) 21.8% | |
| House 3rd Essex | Andy Vargas (D) 52.8% | Shaun P. Toohey (R) 46.2% |