The firing comes after Del Rio signed a four-year contract extension last offseason.
"Today was kind of a microcosm of our season," Del Rio said after the Raiders' 30-10 loss to the Los Angeles Chargers on Sunday. "The opportunities and lack of production really not good enough, really disappointing."
Del Rio seemed to agree that because of his work the team is poised for better things.
"I believe we have developed a solid nucleus," he said, adding that whoever replaces him will have a chance to go to "special places."
He said the Oakland Raiders are his childhood team and he appreciated the opportunity to serve as head coach.
Del Rio became head coach in January 2015 and won 25 games and lost 23 in three seasons, including a 6-10 season this year.
Del Rio said his first two years were great, while this year was a great disappointment.
He said, "I understand it's a results business."
Bay City News contributed to this report.