The 35-year-old left-hander spent three weeks on the bereavement list after his wife, Gabrielle, was found dead on May 20 in the master bedroom of couple's home in the Phoenix area.
Since returning on June 9, Schoeneweis has given up 15 earned runs in nine innings. He is 1-2 with an 8.24 ERA in 38 games this season.
"Obviously this has been an incredibly difficult year," Arizona general manager Josh Byrnes said. "He's done everything he could to deal with a tragedy and to keep playing. At this point, we felt it was a bit overwhelming. He needed a break from it.
"Hopefully he can return to pitch at some point this season. We felt it was necessary and appropriate to do at this time," said Byrnes, who added there is no timetable for a return. "We'll first address real-life issues. We'll see if that will allow him to return to baseball."
A cause of death has not been made public, and an attorney for Schoeneweis said the family has filed suit to keep the records sealed.
Schoeneweis and Gabrielle had three children together, and she also had a daughter before she married the reliever. He has been raising all four children, ages 14, 7, 5, and 2.
"It's obviously been a horrific year for him," Arizona manager A. J. Hinch said. "On a personal level, I can't imagine what he's endured. He has tried his best to be a major league baseball player while going through the worst thing imaginable.
"He's done an incredible job of raising four kids and doing this," Hinch added. "At this point, baseball becomes irrelevant."
Schoeneweis, an 11-year veteran, spent 2007 and 2008 with the New York Mets, who were in Arizona for the second game of a three-game series Tuesday.
Mets manager Jerry Manuel and left-hander Pedro Feliciano said they spoke to Schoeneweis last week, when Arizona played a four-game series at Citi Field.
"My heart goes out to him, his family and his kids. He was a part of us. He gave us everything he had. I'll always have a place in my heart for him," Manuel said. "I gave him a big hug. I told him, 'I don't understand. I don't know. I never felt that.' That's a tough deal."
Arizona recalled left-hander Daniel Schlereth from Double-A Mobile to take Schoeneweis's place on the roster.