The 15-year veteran isn't retiring and said he hopes to find a new team this fall, U-T San Diego reported. Spikes, 36, started all 16 games for the Chargers last season with 79 tackles.
He had one year left on a three-year contract.
Releasing Spikes, a two-time Pro Bowl selection, frees $3 million in salary cap space, giving the Chargers more than $10 million in cap room as the free agency period begins next Tuesday.
"Takeo is a true professional and a class act," Chargers General Manager Tom Telesco said in a statement. "We're grateful for his many contributions to the Chargers organization, both on and off the field, and wish him nothing but the best in the future."
Spikes played with the Cincinnati Bengals, Buffalo Bills, Philadelphia Eagles and San Francisco 49ers since entering the league in 1998.