Magic Kingdom Park and the Epcot Center both opened at 9 a.m.
Disney World's two water parks, Blizzard Beach and Typhoon Lagoon, will remain closed.
Busch Gardens expects to reopen Wednesday in Tampa.
Some attractions may be modified when the parks reopen Tuesday.
Eyewitness News editor Ashley LoFaso captured what it was like at Disney World when Irma arrived in the Orlando area early Monday.
According to CNBC, Walt Disney Company (NYSE:) is planning on opening on Tuesday while SeaWorld Entertainment Inc (NYSE:) issued a statement saying it would reopen its Orlando park Tuesday.
Epcot: 9:00 a.m. - 9:00 p.m.
All Disney Resorts will begin normal operation September 12, 2017 with the exception of Disney's Fort Wilderness Campground and Disney's Saratoga Springs Treehouse Villas. Some areas suffered damage like downed trees and signs, but the theme parks are operating on normal hours, according to the Disney World site, and things appear OK overall thanks to speedy cleanup efforts.
Special events like Mickey's Not So Scary Halloween Party will take place.
"Based on the latest forecasts for Hurricane Irma and keeping safety top of mind, Walt Disney World Resort and Disney Springs will be closed through Monday, September 11", Disney's website read. They're expected to open later in the week.
It was only the sixth time in the resort's 45-year history that severe weather has forced the theme park to close. Disney previously closed during other hurricanes in 1999 and 2004 and was briefly evacuated on September 11, 2001. It's not clear which attractions may be affected.
In Orlando, Walt Disney has not only its amusement parks, but also more than 25 resort hotel to house vacationers.