Beltre, injured in a 5-1 loss against Houston late last month on a slow, short-hopper, was expected to miss the rest of the regular season after an MRI earlier this month showed the Grade 2 strain.
While Beltre is active, he did not play Tuesday night and is expected only to be available as a pinch hitter for now.
"If this had been August, he probably wouldn't be active," general manager Jon Daniels said. "But he's been making progress. Given the roster rules, it made sense to activate him."
The Rangers originally said Beltre was expected to be sidelined for a minimum of four weeks. That would have taken his recovery into the final weekend of the regular season.
But his surprise early return now means help for the stretch run as the Rangers remain within striking distance of the second AL wild-card spot.
Beltre, 38 and in his 20th major league season, has a .315 batting average, 16 homers and 66 RBIs in 80 games this season. He also joined the 3,000-hit club in late July.
To make room for Beltre, the Rangers released right-hander Tyson Ross, who was 3-3 with a 7.71 ERA
In addition to Beltre's return, the Rangers welcomed Willie Calhoun to the lineup. Calhoun, making his major league debut, was the prize return in the trade that sent pitcher Yu Darvish to the Los Angeles Dodgers.