Washington held special elections on November 3, 2015, deciding 4 legislative seats across 2 districts.
Legislature
- House (98 seats): 51 D, 47 R before the election, 0 D, 0 R after.
- Senate (49 seats): 24 D, 25 R before the election, 24 D, 25 R after; control stayed with a bipartisan coalition.
Legislative races
Ballot measures
| Measure | Description | Result |
|---|
| Advisory Vote 10 | Oil spill prevention taxes | Passed (51.32% yes) |
| Advisory Vote 11 | Medical marijuana patient database fees | Passed (58.73% yes) |
| Advisory Vote 12 | Status of tax increase of 11.9 cents | Failed (35.63% yes) |
| Advisory Vote 13 | Tax preferences for certain manufacturers | Failed (36.59% yes) |
| Initiative 1366 | Sales tax decrease/Supermajority vote for tax increases | Passed (51.52% yes) |
| Initiative 1401 | Penalties for trafficking in rare animal species | Passed (70.29% yes) |