The club reinstated the lefty reliever from the restricted list and optioned another left-hander, Daniel Schlereth, to Double-A Mobile in a corresponding move.
Schoeneweis said he felt it was time to return to work after spending the last three weeks tending to the couple's four children and handling other matters.
"The family's good, and it's time for daddy to go back to work," Schoeneweis said before the Diamondbacks played host to the San Francisco Giants.
Authorities have not determined a cause of death for Gabrielle Schoeneweis, 39, who was found dead in the couple's home in suburban Fountain Hills on May 20.
Schoeneweis said he initially considered sitting out the rest of the season before deciding he needed to return.
"It's something that I would feel unfinished for me, personally," he said. "I think my wife would want me to play as well.
"I wanted to make sure that my kids were OK, first, obviously," he said. "They have been doing well. I had a lot of things to take care of. I needed the time to get those things taken care of. I kind of put myself on the back burner. It's been kind of tough on me recently. I'm running out of things to do. [At] 8:30 at night, everybody's asleep."
Schoeneweis said he's relying on family and friends to help him care for the family's children. He and Gabrielle had three children together, and she also had a daughter before she married the reliever. The couple celebrated their 10th anniversary in January.
Schoeneweis had visited Chase Field several times since his wife's death but had not spoken publicly. He tuned up for his return with bullpen sessions and by throwing an inning of extending spring training last Friday.
"We're happy to see him and get him back on our club," manager A.J. Hinch said. "Obviously, we still have heavy hearts for him. I know he's going through a lot.
"As his second family here, we're certainly thrilled to have him back, and we'll provide any support that he needs as his life gets back underway and the normal schedule that he's used to in a baseball life," Hinch said.
Schoeneweis told Hinch that he was available to pitch Tuesday night, when the Diamondbacks opened a three-game series against the Giants. Schoeneweis spoke as if he's looking forward to his work life returning to normal quickly.
"Baseball's pretty distracting," Schoeneweis said. "It takes a lot of concentration and focus, so that'll be good for me personally. It'll be emotional, I'm sure. It's just different. It's not the same. But it's my job and I'm fully confident that I can get the job done."
Schoeneweis, acquired from the New York Mets last winter, is 0-0 with a 2.53 ERA in 19 games.