The former New Orleans Saints defensive coordinator has been allowed to resume work in the NFL after serving a season-long suspension for his part in the bounty scandal, which saw Saints players offered financial incentives to injure their opponents.
Williams told reporters: "I met with the commissioner (Roger Goodell) last week, and we had a good talk. I thank him for my reinstatement back in the league.
"I'm thankful and grateful and will immediately begin to work tirelessly to fulfill the commitments to this organisation and the Nashville community to help the Tennessee Titans football team be successful.
"I take full responsibility and apologise for my previous actions, and I've used this year to reorganise my life and put focus on positive energy and positive ways to inspire, coach and motivate in this profession. I'm here to put my focus and my energies into working tirelessly on behalf of the Titans and making as much of a positive impact in every way possible as I can for them."
Williams previously worked at the Titans from 1997 to 2000 as defensive coordinator.