Surrounded by military guards of honor, the Venezuelan leader boarded a Havana-bound plane at Maiquetia International Airport at about 9:15 pm local time (0145 GMT Sunday).
Earlier in the day, Chavez said in a message broadcast on radio and television that he was planning to start radiation therapy inHavanaon Sunday, adding that his treatment was expected to continue "four or five weeks."
The news came with Chavez already campaigning for re-election later this year.
Chavez, 57, underwent surgery inHavanaon February 26 to remove a cancerous tumor around the pelvis, the same area from where a first tumor was extracted in June last year.
Officials inCaracashave never specified what type of cancer the president is suffering from, but they have denied the disease has spread to other organs.
Latin America's highest-profile leftist leader, who has been in power since 1999, faces a strong challenge in the October 7 presidential election from 39-year-old Henrique Capriles, the candidate of a unified opposition.
Chavez said the radiation therapy would be applied to the same areas where he had had surgery, without specific details.
He was "eating and moving without any difficulty," following last month's operation, he added.
Chavez made the announcement in the middle of a council of ministers in theMirafloresPalace, where he told his team that he would remain active in the government.
"I will be calling, signing, reading," he said.
"Today, radiation therapy and gradually I will again assume my role at the forefront and succeed."
Chavez, who is running for a third term as president in the October 7 election, has ruled out the possibility of a replacement candidate.
He faces a strong challenge from 39-year-old Henrique Capriles, the candidate of a unified opposition.
Chavez has usedVenezuela's vast oil wealth on popular social programs and to help keep afloat his communist allyCuba, even as he courted anti-US allies fromIrantoLibya.