The Chase Center and the band issued statements at 7:20 p.m. for the 7:30 p.m. show, forcing thousands of fans inside the arena and waiting in lines outside to exit the building.
"We are unable to perform as scheduled tonight at Chase Center in San Francisco due to a medical emergency involving a member of our band," Earth, Wind & Fire shared on social media.
Officials have not released information regarding which band member is sick or their current medical condition.
The Chase Center say original tickets remain valid for the rescheduled date, and full refunds are available for those unable to attend.
Lionel Richie himself had to postpone two concerts in June after an episode of dizziness at a show.