Matt Shoemaker, meanwhile, was expected to miss at least one turn in the rotation because of a mild strain on his left side.
Angels manager Mike Scioscia revealed the injury updates Tuesday, one day after his team became the first in the majors to clinch a playoff spot this season.
Pujols is playing first base and batting third while Hamilton is batting sixth as the designated hitter Tuesday against the Seattle Mariners.
On Monday night, Pujols wrote off the cramp to dehydration on another hot day in Orange County, and had said he expected to play Tuesday.
Hamilton is returning a day earlier than expected. On Monday, manager Mike Scioscia said he considered Hamilton's workout a "breakthrough" and had expected him to return as the DH on Wednesday night.
Pujols is hitting .274 with 26 homers and 97 RBIs while Hamilton is batting .263 with 10 homers and 44 RBIs for the AL West-leading Angels.
Shoemaker, who has set a franchise rookie record with 16 wins, was removed from Monday night's 8-1 victory over the Mariners after 7 2/3 innings and had an MRI. He is 7-0 with a 1.29 ERA in his last eight starts since losing 2-1 to the Dodgers on Aug. 6.
In 20 starts overall, the right-hander is 14-3 with a 2.89 ERA after beginning the season in the bullpen.
Information from The Associated Press is included in this report.
Angels Clinch Playoff Spot With Win Over Mariners
Matt Shoemaker picked up his 16th victory of the season in the Angels' 8-1 win over the Mariners.