Will Espero served in the Hawaii State Legislature from 1999 to 2018. He served in the state House of Representatives for 3 years and the Hawaii State Senate for 16 years. Espero had leadership roles as senate vice-president and majority floor leader.

In his legislative Career, Espero introduced and passed over 100 bills and resolutions. He had a significant impact in passing police reform measures, prison reform bills, the medical cannabis dispensary program, banning chemicals in sunscreen, and affordable housing initiatives.

Will Espero also worked in the administration of Mayor Frank Fasi prior to his work at the state capitol. He was the Executive Secretary of the Neighborhood Commission which oversees Oahu's neighborhood board system.