De Leon announced his plans Monday morning. The Eastside council seat is being vacated by Councilman Jose Huizar.
The 52-year-old De Leon already has the support of nearly two dozen elected officials in Los Angeles.
De Leon served in the legislature from 2006 until last year. He went on to run unsuccessfully against Sen. Dianne Feinstein in November.
De Leon says he would be honored to continue his work at the local level.