The Orioles let a four-run cushion dwindle to 5-4 in the eighth but held on for their fifth straight home win over the Rays, dating back to last year.
Desmond Jennings homered on the game's first pitch for Tampa Bay, and Kelly Johnson and Evan Longoria connected off Pedro Strop in the eighth. But the Rays could muster only six hits against Jake Arrieta and five relievers.
Last-place Tampa Bay has lost four straight and seven of eight. Although the Rays scored more runs than they totaled in their previous three games, they went 0 for 6 with runners in scoring position and are 1 for 34 in that situation over their past eight games.
With a 4-9 record, Tampa Bay has matched the worst start in franchise history (2001 and 2005).