The Popovichs were married for more than 40 years. Erin was previously ill for an extended period, according to ESPN.
"We mourn the loss of Erin," Spurs general manager R.C. Buford said in a statement. "She was a strong, wonderful, kind, intelligent woman who provided love, support and humor to all of us."
Erin and Greg had two children and two grandchildren.
Popovich has coached the Spurs for 22 years. He is 69-years-old. The Spurs battle the Golden State Warriors in Game 3 of their first round Western Conference playoffs series at 9:30 p.m. Thursday at the AT&T Center in San Antonio, Texas. Golden State leads the series 2-0.
The future Hall of Fame coach did not mention his wife when speaking to reporters on Wednesday at the Spurs' practice session.
Condolences poured out from those tied to the NBA after the news spread.
I was shocked and saddened to hear on @NBAonTNT of the passing of #ErinPopovich wife of @spurs head coach Gregg Popovich, died today. They were married four decades. My heart goes out to him & his family. @NBA— TheBillRussell (@RealBillRussell) April 19, 2018
"I was shocked and saddened to hear on @NBAonTNT of the passing of #ErinPopovich wife of @spurs head coach Gregg Popovich, died today," Bill Russell tweeted. "They were married four decades. My heart goes out to him & his family."
The Spurs could turn to assistant coach Ettore Messina if Popovich misses any games during the playoffs.