The Bradford-born singer left the stage during the band’s Perth performance, leaving his bandmates to cover his solo sections.
A spokesperson for the band tells The Sun: “Zayn was taken ill during the show but it's nothing serious.
"He wasn't feeling that great beforehand but he tried to get through the performance as well as he could.
"Everyone is hoping he’ll be well enough for their next gig."
The band have just a few days off before performing more concerts in Japan, which are followed by stop-offs in Africa and Dubai, before UK gigs in June.
Before the tour, the band enjoyed some much-needed time off, and Harry Styles celebrated his 21st birthday with a star-studded bash in LA.