| District | Incumbent | This race |
| Chamber | No. | Representative | Party | Firstelected | Results | Candidates |
| House | 33Position 1 | Tina Orwall | Democratic | 2008 | Incumbent resigned December 10, 2024, after being appointed to the State Senate.New member to be elected November 4, 2025.Democratic hold. | ▌Kevin Schilling (Democratic) 50.2% ▌Edwin Obras (Democratic) 47.3% ▌Write-in 2.6% |
| House | 34Position 1 | Emily Alvarado | Democratic | 2022 | Incumbent resigned January 21, 2025, after being appointed to the State Senate.New member to be elected November 4, 2025.Democratic hold. | ▌Y Brianna Thomas (Democratic) 96.9% ▌Write-in 3.1% |
| House | 41Position 1 | Tana Senn | Democratic | 2013(appointed) | Incumbent resigned January 15, 2025, to lead the Washington Department of Children, Youth, and Families.New member to be elected November 4, 2025. | ▌Janice Zahn (Democratic) 69.4% ▌John Whitney (Republican) 30.4% ▌Write-in 0.2% |
| House | 48Position 1 | Vandana Slatter | Democratic | 2017(appointed) | Incumbent resigned January 7, 2025, after being appointed to the State Senate.New member to be elected November 4, 2025. | ▌Osman Salahuddin (Democratic) 68.2% ▌Dennis Ellis (Republican) 31.6% ▌Write-in 0.2% |
| Senate | 5 | Bill Ramos | Democratic | 2024 | Incumbent died April 19, 2025.New member to be elected November 4, 2025. | ▌Victoria Hunt (Democratic) 54.5% ▌Chad Magendanz (Republican) 45.3% ▌Write-in 0.2% |
| Senate | 26 | Emily Randall | Democratic | 2018 | Incumbent resigned December 8, 2024, to become a U.S. representative.New member to be elected November 4, 2025. | ▌Deborah Krishnadasan (Democratic) 52.7% ▌Michelle Caldier (Republican) 47.3% ▌Write-in 0.1% |
| Senate | 33 | Karen Keiser | Democratic | 2001(appointed) | Incumbent resigned December 10, 2024.New member to be elected November 4, 2025.Democratic hold. | ▌Y Tina Orwall (Democratic) 94.5% ▌Write-in 5.0% |
| Senate | 34 | Joe Nguyen | Democratic | 2018 | Incumbent resigned January 15, 2025, to lead the Washington State Department of Commerce.New member to be elected November 4, 2025.Democratic hold. | ▌Y Emily Alvarado (Democratic) 96.8% ▌Write-in 3.2% |
| Senate | 48 | Patty Kuderer | Democratic | 2017(appointed) | Incumbent resigned January 7, 2025 to become the Washington State Insurance Commissioner.New member to be elected November 4, 2025.Democratic hold. | ▌Vandana Slatter (Democratic) 55.9% ▌Amy Walen (Democratic) 42.3% ▌Write-in 1.8% |