Police said there were injuries among those in one of the helicopters.
The Queensland Ambulance Service said 13 patients were being assessed.
One of the helicopters managed to land successfully after the aircraft “came into contact with each other” about 2pm (3pm AEDT), police said.
Footage of the scene shows wreckage strewn across a sand island close to the coast.
John, who didn’t give a last name, told Nine radio station 4BC the crash happened “just outside the theme park”.
“(I) didn’t really know what it happened but there was a massive bang,” he said.
“And yeah, they’ve closed that side of the park now so people can’t look out the side into the water there. Pretty scary stuff actually.”
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John said he saw a woman and her son “in tears” at the Sea World helipad.
9News weather reporter Luke Bradnam said he saw “ambulance after ambulance” rushing to the “tragic” and “unexpected” incident.
“We see so many choppers in the air here on the Gold Coast Broadwater border but in my memory, I cannot remember anything like this ever occurring,” he told the radio station.
Emergency services shut Seaworld Drive, Main Beach, urging pedestrians and drivers to avoid the area.
Footage from the scene shows wreckage strewn across a sand island close to the coast.
A Sea World spokesman said the company was working with authorities to find out more information before commenting further.
Paramedics said multiple resources had been sent to the “major incident”.