The purpose of the Senate is to: represent the people of Washington; initiate legislation affecting public policy, act on legislation passed by the House of Representatives or by initiative to the Legislature; pass a biennial budget that pays for the day-to-day operations of state government (including federal funds and dedicated funds); a budget that pays for transportation activities such as designing and maintaining roads and public transit and a budget to acquire and maintain state buildings, public schools, higher education facilities, public lands, parks, and other state assets; provide for the levying and collecting of taxes and other revenue to support state government and to assist local governments; appropriate funds for these purposes; and confirm certain gubernatorial appointments.

The mission of the Senate is to exercise legislative powers granted by the state Constitution; to represent and provide leadership for the people of the state of Washington; to enact laws and oversee their administration; and to provide for the public well-being while protecting and maintaining the rights of the individual.