Venezuelan officials said Tuesday they could not immediately verify the call, but a recording provided by the Cuban-American radio announcers contains a voice that sounds like Chavez.
The tape appears to have Chavez, who is struggling to end a month-old national strike by opponents, happily answering what he thought would be a friendly call Monday morning from Castro, one of his closest allies.
But on the other end of the line were WXDJ-FM disc jockeys Joe Ferrero and Enrique Santos, who ended the conversation by calling Chavez "terrorist" and "animal," along with a few expletives.
During the call, they played disjointed snippets of a private conversation between Castro and Mexican President Vicente Fox, which the Cuban leader released last year.
"We usually call (regular) people," Ferrero said. "We never thought that we would be able to talk to Chavez. We thought maybe we'd be able to talk to a secretary."
He said they had tried about 10 times since Friday to bluff their way past Chavez' aides at the Venezuelan presidential palace.
But on Monday, Ferrero said, he and a woman posed as telephone operators and told a Chavez secretary that they needed the president's personal phone number to connect him with Castro, who supposedly was in a hidden location and could not receive calls. A recording of Castro's voice was heard in the background.
The announcers said the secretary finally consented, and they called Chavez with their tape of Castro ready to roll.
"Hello Fidel?" Chavez answered, according to a copy of the call provided by the announcers.
"Yes. Did you receive my letter?" Castro asked.
After greeting Castro, Chavez said: "Yes, I received everything fine."
"I am ready to cooperate with you," the voice of Castro replied.
After an exchange about the day of the week, Santos broke in and said they were calling from Miami.
"Get out of Venezuela, (expletive) terrorist! ... Animal, assassin, (expletive)!" Santos said before hanging up.
Venezuelan Information Minister Nora Uribe said Tuesday that she was not immediately able to confirm the call. Venezuelan officials in Washington and Miami did not return calls Tuesday.
Ferrero said the station was inundated with congratulatory phone calls, but Santos said WXDJ owner Raul Alarcon Jr. was "not very happy."
"He was a little bit upset that my partner began blowing off the president of Venezuela," Ferrero said.
However, the pair said they will not be disciplined. Alarcon did not return a call seeking comment.