Lula arrived at the Sirio-Libanes Hospital just days after his condition was diagnosed. Accompanied by his wife Marisa Leticia, the Brazilian leader skirted dozens of journalists who had gathered at the door of the hospital awaiting his arrival.
One day earlier, doctors told reporters that Lula was ready to commence with his treatment, despite having only last week received his cancer diagnosis.
"He is in good spirits and on board, committed, and that is key to the success of any treatment," Dr. Roberto Kalil Filho told reporters assembled outside Lula's home in Sao Bernardo do Campo.
He added that the popular former leader, who was Brazil's first democratically elected leftist president, has a greater than 80 percent chance of a making a full recovery.
Officials in Brazil announced last week that the 66-year-old Lula was diagnosed with cancer of the larynx following a series of tests.
"It is a localized tumor in the larynx, without ramifications, and it is perfectly treatable," Paulo Hoff, one of the doctors treating Lula, told the daily O Estado de Sao Paulo on Sunday.
Jose Crispiniano, a spokesman for the Citizenship Institute that Lula created after leaving office, said the ex-president, a former smoker, went to the hospital on Friday complaining of throat pain.
Lula, who is known for his raspy voice, was "even hoarser than usual," he said.
News of Lula's cancer came as a shock to Brazilians, who adore the former metal worker and labor activist, who left power with a soaring 80 percent approval rating after two consecutive terms from January 2003 to December 2010.
His social programs helped lift 29 million Brazilians out of poverty, and his foreign policy helped turn Brazil into a global power player.