"We will continue our battle, and we will continue winning," the Venezuelan leader tweeted shortly before takeoff from Caracas. "A heartfelt embrace to my beloved and heroic people. We will keep living and keep winning."
The Venezuelan president said earlier that he would spend several days in Cuba.
Under the constitution, Chavez is required to seek permission from the National Assembly if he is to stay outside the country for more than five days.
The announcement of Chavez's return to Cuba, however, came only two days after he arrived home from the island late Wednesday after completing a third course of radiation therapy.