Seattle is sending minor league right-handers Andrew Moore and Tommy Romero to Tampa Bay.
The veteran Span was tied for the team lead with 28 RBIs. He'll join a beat-up Mariners team that is without Robinson Cano (PED suspension) and Dee Gordon (10-day disabled list, broken toe).
Colome, a 2016 All-Star, had 28 saves for Tampa Bay to go with a 4.15 ERA. He'll likely set up Mariners closer Edwin Diaz, who entered Friday with an MLB-best 17 saves this season.
"This is a trade that makes us a more complete club in the present while also offering impact beyond this season," Mariners general manager Jerry Dipoto said in a statement. "Alex Colomé brings an all-star resume, fortifying what we believe is an already solid back end of the bullpen. Denard Span adds length to our lineup as a steady and smart player with consistent on-base skills in addition to a veteran presence that enhances our environment."
Moore, 24, is 3-1 with a 3.04 ERA in nine starts for Double-A Arkansas this season. Romero, 20, is 3-3 with a 2.45 ERA in nine starts for Class-A Clinton.
The Rays alsoacquired right-handed pitcher Wilmer Font from the Oakland A's in exchange for minor league pitcher Peter Bayer.