General Sarath Fonseka arrived at Bandaranaike International Airport and was immediately driven away under tight security, an airport official said.
"He arrived this morning in a commercial flight and was escorted out of the airport by his security convoy," an official said.
The Foreign Ministry here said he ended his US visit without being quizzed by the Department of Homeland Security, which had asked to interview him about alleged war crimes during the final stages of fighting this year.
Fonseka, who holds US permanent residency, had travelled to Oklahoma to visit his two daughters.
Sri Lanka had feared the department would try to force Fonseka to provide evidence against Defence Secretary Gotabhaya Rajapakse, who holds US citizenship, over alleged human rights violations.
The defence secretary is the younger brother of President Mahinda Rajapakse.
Sri Lankan troops in May killed the leaders of the Tamil Tigers, ending one of Asia's longest-running and bloodiest insurgen