Chavez appeared on state television early Thursday at a meeting with aides, and said his plane touched down in Venezuela shortly before midnight.
"Thanks to God, I've withstood the treatment very well," Chavez said. "Let's hope that's the case next time."
He said the radiation treatments have been administered for five days in a row and that he will now stay in Venezuela until Saturday, when he plans to return to Havana for the next round. He said this week's treatments have been the first of five rounds.
Chavez has said the radiation treatments are intended to prevent any new cancer threat after a surgery last month that removed a second tumor from his pelvic region. He had another tumor removed from the same location in an earlier operation in June.
He said that on Wednesday, his friend and mentor Fidel Castro came to visit with him after seeing Pope Benedict XVI. Chavez said he and Castro took a ride around Havana together, and Castro showed him some farmland where agricultural research is being carried out.
Chavez said Castro also told him about his conversion with the pope. He said that according to Castro, the conversation with the pope was "very cordial and positive for Cuba and for our (Latin) America, and for the world, too."
Chavez said Castro was also impressed that despite the pope's age, he maintains "a very heavy schedule."