Financial terms were not revealed. The four-year deal includes a fifth-year team option, which is standard for all first-round draft picks.
Mariota was the last unsigned first-round pick from this year's draft. The sides had been at odds over offset language, which allows a team to recapture guaranteed money if a player is released and signs with another team.
The Titans and Mariota agreed to partial offset language, a league source told ESPN NFL Insider Adam Caplan.
The Titans tweeted a photo of the signing:
"We are glad to have the deal with Marcus done, and I'd like to thank both Marcus and his representatives for their diligence in working with us to finalize this contract," Titans general manager Ruston Webster said in a statement released by the team. "We were confident that Marcus would be under contract before training camp, and we look forward to him starting his career on time with his teammates when we open camp next week."
The Titans report to training camp July 30 and have their first practice July 31.
Now Mariota, the No. 2 overall pick and Heisman Trophy winner out of Oregon, can focus on getting a grasp of the Titans' offense and beating out Zach Mettenberger to be the team's starting quarterback this season.
"Thank you to the Tennessee Titans organization as well as my agent for making a dream come true," Mariota said in the statement. "I am very grateful and honored to have this opportunity. I look forward to the future with the my teammates, and I'm truly excited to be part of this team."