Witnesses say the 84-year-old Nelson was apparently having trouble breathing during the song "Whiskey River" and immediately canceled the show.
A representative for the beloved country singer said Nelson had "a bad cold or the flu" and has gone home to Texas to recover.
Nelson's shows through January 14, which included another California date and a two-night residency in Las Vegas, have been postponed.
The two shows at the The Chelsea at The Cosmopolitan of Las Vegas have been rescheduled for October 19 and 20.
Another show scheduled for The E Center in Laughlin, Nevada, was rescheduled to October 12.
Fans with tickets to the January 10 show at Graton Resort and Casino were still awaiting a rescheduled date.
Nelson is scheduled to be on the road again, starting February 7 in Macon, GA.
Get all of Nelson's tour dates here.
Rolling Stone points out that this is not the first time in recent memory the country legend has called off a performance in progress due to respiratory issues.
In August of 2017, he cut short a concert in Salt Lake City because he was having trouble breathing. At the time, the singer said it was due to the city's high altitude.
In February of 2017, Nelson also canceled a handful of dates due to illness.
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