In a corresponding move, Washington optioned outfielder Matt den Dekker to Triple-A Syracuse.
Werth missed the season’s first six games after recovering from surgery on the AC joint in his right shoulder in January.
The Nationals went 2-4 without him and have scored only 13 runs this season, tied for the fewest in MLB.
"I feel good. I haven't had a lot of at-bats, but I'm about to get a bunch," Werth said to MLB.com. "It was a tough January, February, March. I was just trying. I'm glad to be back. I felt really good."
Werth went 1-for-6 with one home run on a rehab assignment with Single-A Potomac.
Werth has spent the past four seasons in Washington, and last season hit .292 with 16 home runs and 82 RBI in 147 games.
- Scooby Axson