Popovich has missed the past six games with what was initially described as an undisclosed health issue.
In a team statement, the Spurs revealed he had suffered a stroke on November 2nd at the team's arena ahead of a home win over the Minnesota Timberwolves.
Assistant Mitch Johnson stepped in as interim head coach in Popovich's absence and has led the Spurs to a 2-3 record in those five games.
San Antonio said no timeline for his return has been determined.
Popovich, the oldest coach in NBA history, is the league's all-time leader in victories with 1,390 regular-season wins and another 170 post-season triumphs.
He has guided the Spurs to five NBA titles in his 29 seasons at the helm.
