The band is currently touring Down Under with Kiss and Thin Lizzy, and they were playing a second show at Sydney's Allphones Arena on Sunday when Neil was taken ill.
The show was cut short and the singer was admitted to a local hospital to treat "internal pain".
Neil's bandmate Nikki Sixx explained the drama to fans in a post on Twitter.com, writing, "Sorry Sydney for a short set tonight but Vince had to be rushed to the hospital for internal pain. Will update you on his progress."
No more details about Neil's condition were known as Wenn went to press.