A portrait of Hollywood star Heath Ledger painted weeks before his death has won an Australian art award.

The painting features a bare-chested Ledger staring from the canvas as two images of the actor whisper into his ears.

On Thursday, it was awarded a secondary prize by the Art Gallery of New South Wales in its annual national portrait competition. Sydney artist Del Kathryn Barton won first prize with her self-portrait.

"Heath" by Vincent Fantauzzo was the popular choice among the 32,000 who saw the exhibition.

Ledger died of an accidental prescription drug overdose in January. He was 28.