Ledger, who died last January at age 28 from an accidental prescription drug overdose, earned the Globe for his portrayal of the malevolent Joker in the latest Batman adventure, "The Dark Knight."
"All of us who worked with Heath on 'The Dark Knight' accept this with an awful mixture of sadness and incredible pride," the movie's director, Chris Nolan, said as he took the stage to pick up Ledger's prize. "He will be eternally missed, but he will never be forgotten."
Ledger's father, Kim, who was unable to attend the Globes ceremony, told People magazine he thinks "it's wonderful" his son is being honored for his work.
"We are overjoyed for him," said Ledger, who lives in Australia.
Also nominated in the best supporting actor in a film category were Tom Cruise and Robert Downey Jr. for "Tropic Thunder," Philip Seymour Hoffman for "Doubt" and Ralph Fiennes for "The Duchess."