Yarbrough (1-3) followed opener John Curtiss in the second inning and gave up one run and five hits over 5 2/3 innings for his first win since Aug 11, 2019 at Seattle.
The Rays are 3-4 in a stretch of eight straight games against last place teams.
Washington got a sixth-inning RBI grounder from Kurt Suzuki.
Yarbrough’s skid consisted of all starts. The lefty has had success coming out of the bullpen, going 23-5 in 47 career relief appearances, many following an opener.
Manuel Margot chased Aníbal Sánchez (2-5) with a bases-loaded, one-out RBI infield single in the fifth that put the Rays up 3-0.
Kiermaier had missed the previous two games due to general body soreness.
Lowe homered and Kevan Smith had an RBI single as the Rays went up 2-0 in the second.
Sánchez allowed six runs and seven hits in 4 1/3 innings.
Washington’s Juan Soto was 1 for 4 with a double. Since returning to the lineup on Sept. 8 following a stint on the injured list, Soto is 6 for 18 and has reached base safely in 16 of 28 plate appearances.
Rays: RHP Oliver Drake (right biceps tendinitis) was reinstated from the 10-day IL. … 1B Ji-Man Choi (left hamstring strain) went on the 10-day IL. … C Mike Zunino (left oblique strain) is taking live at-bats at the alternate training site.
Nationals RHP Austin Voth (0-5) will start the series finale on Wednesday. Tampa Bay has not announced its starter.