The election will be held on November 4, 2014.
Brown released an open letter online to the citizens of California Thursday morning. He outlined accomplishments such as turning a budget deficit into a surplus and improving the state's credit rating, on-time budgets, bipartisan legislative cooperation, and restoration of education funding, among others.
In the statement, Brown outlines future goals for his office, including addressing prison and immigration reforms, as well as pension reform, infrastructure repair and investment, and clean energy. He also committed to working toward sustainable water policies amid this year's historic statewide drought.
Brown, 75, previously served as California governor from 1975 to 1983. He was elected again in 2010.
Democrats hold every statewide office and control both chambers of the Legislature. Polls show Republicans in the race so far remain unknown to many Californians. Brown's rivals include former U.S. Treasury official Neel Kashkari and state Assemblyman Tim Donnelly of Twin Peaks, both Republicans.
The Associated Press contributed to this report.