The standoff began when the suspect told the hotel desk he was heavily armed and holding a hotel employee along with his 4-year-old boy hostage, police said Thursday.
The hotel evacuated guests from several floors in the affected wing of the 378-room Boardwalk Inn. Police halted the flow of traffic into the hotel.
Authorities said the man was at Disney World on vacation and that he had threatened to kill himself.
Suspect asked for FBI hostage negotiator
"We also know that he called the Orlando FBI office and asked for their hostage negotiator," said Orange County, Florida, Sheriff Kevin Beary, adding that the FBI agent was at the scene.
"We've been told he's heavily armed," Beary told reporters.
Beary said there could be more than two hostages, and negotiators were trying to keep the man "calmed down."
Beary said authorities were trying to find members of the suspect's family to help in the negotiations.
"We want a peaceful solution; it's very tense," Beary said. "We don't want anybody hurt."
Capt. Steve Jones of the sheriff's department said, "The main thing is he wants to talk to his wife, who is separated from him."
SWAT team nearby when incident began
Asked if the suspected gunman might be watching television news coverage of the standoff, Beary said, "He's not watching television, 'cause we've done some things so he can't watch television."
Beary said that was done for the safety of law officers at the site.
There were no reports of any shots being fired.
"Law enforcement is in total control of the situation," said Disney World spokesman Bill Warren. "It is a hostage situation. It's contained to one room of the hotel. Our guests and employees have been evacuated from the immediate area."
The standoff was at the Boardwalk Inn directly across the street from Disney-MGM Studios, not far from Epcot. Beary said police SWAT officers had been putting on a demonstration for Boy Scouts nearby when the problem was reported.
"We were right there off (Highway) 417 at the range," he said.
"We are in constant contact with the man," sheriff's department spokesman Jim Solomons said.
"Our first priority of course, is the safety and welfare of our guests," Warren said.
Reuters contributed to this report.