The Rays agreed to a one-year, $8.5 million contract with Jansen on Friday, Robert Murray of FanSided.com reports.
Jansen will be the catcher Monday when the continuation of suspended game between the Red Sox and Blue Jays resumes, Ian Browne of MLB.com reports. The two teams will continue a game that was suspended June 27.
Jansen started at catcher and went 2-for-4 with an RBI in Wednesday's 3-2 extra-inning win over the Mariners.
Jansen started at designated hitter and went 2-for-3 with a walk in Sunday's 8-2 loss to the Yankees.
The Blue Jays traded Jansen to the Red Sox on Saturday, Jeff Passan of ESPN.com reports.
Jansen isn't in the Blue Jays' lineup for Saturday's game against the Rangers.
Jansen is not in the lineup for Wednesday's game versus the Rays.
Jansen is out of the lineup for Tuesday's game against Tampa Bay.
Jansen is not in the lineup for Friday's contest versus the Tigers.
Jansen is out of the lineup for Saturday's game against the Diamondbacks.