Universal Studios Florida and Islands of Adventure hit capacity just after 8 a.m. and stopped admitting new guests. The parks also hit capacity shortly after opening on Tuesday. Guests were asked to check ahead of time before heading out to the parks.
Health officials are monitoring crowd sizes because of COVID-19.
They say Florida has a positivity rate of over 26%.
That means more than one in four coronavirus tests are returned positive.
But public health experts say there is no evidence COVID-19 outbreaks have been linked to any theme parks.
The resort tweeted that it started admitting new guests again by early afternoon.