A member of the public alerted security staff who managed to contact the owners.
The family reportedly told staff they couldn't leave to get the animal for half an hour.
"I know it's not an extremely hot day today, but the dog has been left on the hot tar," the woman who found the animal told the Bulletin.
"It's clearly trying to escape the heat by getting shade from underneath the car.
"It's not right."
Temperatures reached 24.4C on the Gold Coast on Sunday.
Another dog that was allegedly reported to staff was left in the back of a ute tray for over three hours.
A Sea World spokesperson told news.com.au incidents like this rarely occurred at the park.
"We were reported to two incidents of dogs in our carpark on Sunday, and our team were monitoring them while trying to get in contact with their owners," the spokesperson said.
"This is not something which happens regularly at our theme parks, however we would encourage people to leave their pets at home when visiting our properties.
"Our team are trained to call the RSPCA or emergency services if they spot an animal in distress in our carparks."