The team on Friday inked the fourth-year safety to a two-year contract extension that will keep him in San Francisco through 2020.
NFL Network Insider Ian Rapoport reported that Tartt's extension is worth $13 million -- and up to $15 million with incentives -- according to a source.
A second-round pick in 2015, Tartt appeared in 39 games for the Niners before finishing last season on injured reserve with a broken forearm.
"Since we arrived last year, Jaquiski has impressed us with his play, his work ethic and the kind of teammate he is," 49ers general manager John Lynch said in a statement released by the team. "We believe he's a natural fit in our defensive system, and his abilities will allow him to flourish. It is always exciting when we are able to extend our own young players like Jaquiski who are dedicated to their craft, this team and our community."
Tartt is a big-bodied, hard-hitting backstop who figures to play a central role for years to come in the team's Robert Saleh-led secondary. Chalk it up as a smart move by Lynch and friends.