The Los Angeles County Board of Supervisors extended the reward Tuesday, which was set to expire.
Iran Moreno-Balvaneda was hit by a stray bullet that came through his window while he played video games in his bedroom in November 2021.
Police say several shots were fired in the area when a single bullet entered the home, striking the teen.
He later died at a hospital, according to police.
"The grief and loss felt by his family, friends, teachers and community is unimaginable," said L.A. County Supervisor Kathryn Barger in a statement. "I'm extending this $20,000 reward with the hope that those involved in this shooting will be identified and prosecuted. Justice for Iran and his family must be served."
Anyone with information is urged to contact Pasadena Police at 626-744-4241 or Crime Stoppers at 800-222-TIPS (8477).
You can also submit a tip online on the Crime Stoppers website.