In the Assembly, Papan serves as Chair of the Assembly Committee on Water, Parks & Wildlife and serves on the Committees on Transportation and Governmental Organization & Environmental Safety and Toxic Materials.

Prior to her election to the State Assembly, Papan served as mayor and city councilmember for the City of San Mateo where she was a recognized regional leader championing investment in infrastructure, transit and climate adaptation among many policy pursuits.

As a member of the State Assembly, Diane is focused on investing in strategies to address climate change and the related challenges of flooding, drought, and wildfires, as well as water quality, women's health, accessible and quality healthcare services, gun safety, affordable housing, and access to quality public schools.

Papan is a native of San Mateo County, raised in both Daly City and Millbrae, California. She earned a B.A. in political science from the University of California, Los Angeles, in 1985 and a J.D. from the University of California, Hastings College of Law in 1988. Her career experience includes working as an attorney in several different firms, including her own private practice representing small businesses. She also works as an executive director of the nonprofit John's Closet in Daly City, providing new clothing to children in need.

Papan and her husband Dan are proud parents of a teenage daughter.