The test result was reported as Utah's game against the Thunder in Oklahoma City was about to begin. The game was abruptly postponed and the players were effectively quarantined in the locker room area.
The league said the affected player, believed to be French defensive standout Rudy Gobert, was not at the arena and was being treated by health officials in Oklahoma City.
"The NBA is suspending game play following the conclusion of tonight's schedule of games until further notice," the league said. "The NBA will use this hiatus to determine next steps for moving forward in regard to the coronavirus pandemic."
The Jazz issued a statement saying the player had flu-like symptoms but initially tested negative for influenza and a respiratory infection.
The decision was made to test again for COVID-19, for which he tested positive.
"A preliminary positive result came back right before tip-off of the Utah Jazz-Oklahoma City game," the Jazz statement said. "The decision was correctly made by the NBA to postpone the game."
The league and the team have declined to name the player, but Denver Nuggets coach Mike Malone told reporters he believed it was Gobert, who was listed first as questionable for the game and then as out with illness.
"Rudy Gobert. You think it is not going to affect us, we are NBA," said Malone. "One of our players has the coronavirus.
"Who knows what that means for their team and the other teams that have been with them."
- 'This is crazy' -
Gobert angered members of the Jazz media on Monday when he deliberately touched every microphone at a news conference, in what appeared to be a show of bravado about the disease.
Team owners had been discussing Wednesday how the league should respond to the coronavirus outbreak.
Dallas owner Mark Cuban was sitting courtside at the Mavericks' game against the visiting Nuggets when he got the news on his phone.
"I thought this is crazy. It can't be true," Cuban said. "It is like out of a movie. Unreal."
Upon learning the season was being suspended, Cuban immediately walked over to the bench to let the team officials know.
"It is not about basketball and money. This is exploding to the point where I think about the families. We are making sure we are doing this the right way," he said.
"The idea that a couple of players have it... it is stunning."
Earlier NBA team owners and league officials had been wrestling with how to manage in the face of the outbreak, considering not only postponing games, but also playing in empty arenas.
The Golden State Warriors had confirmed they would host the Brooklyn Nets on Thursday in San Francisco behind closed doors after San Francisco city officials announced a two-week ban on all gatherings of more than 1,000 people.
The league-wide decision was made after the confusing scenes in Oklahoma City, where Jazz and Thunder players took the court to warm up, but shortly before the scheduled tip-off were sent to their locker rooms and police began to clear the Chesapeake Energy Arena.
Fans were told only that the game was postponed due to "unforeseen circumstances" before they were herded out of the arena.
Gobert's teammate Emmanuel Mudiay was also listed as suffering from an undisclosed illness on the team's injury report.
- 'Unprecedented' -
Six NBA games were scheduled for Wednesday. Four were underway when the game in Oklahoma City was called off, and a later game between the New Orleans Pelicans and Kings was also cancelled. The decision was made because one of the officials had worked a Utah game earlier in the week.
"It's unprecedented," Detroit coach Dwayne Casey -- whose Pistons fell to the 76ers in Philadelphia -- said of the decision to suspend the season. "I think it's the prudent thing to do."
Miami Heat coach Erik Spoelstra said the virus outbreak is much bigger than basketball.
"Stunned," Spoelstra said after his team lost to the visiting Charlotte Hornets.
"It's a very serious time right now. I think the league moved appropriately," added Spoelstra.
Cuban said he was thinking of the safety and health of his family members.
"This is global pandemic. Peoples' lives are at stake. I am more worried about my kids and my 82-year-old mother than when we play our next game."
Cuban spoke directly to the Mavs' players after the game, telling them to remain in Dallas and don't invite friends in from out of town.
"We expect you to stay in Dallas and I was very specific to say who you talk to, is very important. Bringing people in from out of town because you have down time is not going to work."
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