Pink was hospitalized in Sydney on Monday just hours before she was scheduled to perform in the Australian city.
"Pink was admitted to hospital in Sydney on Sunday night, suffering from dehydration," concert promoter Live Nation said in a tweet.
"She was treated and discharged. She was readmitted to the hospital today and diagnosed with a gastric virus. Pink will remain in hospital overnight, continuing her treatment and recovery."
Pink previously caught flak for canceling her first Sydney show on Friday.
Page Six says she then "battled through" her Saturday Sydney show before going to the hospital on Sunday.