The late Peter Finch won the best actor Oscar a little more than two months after his death in January 1977 for his role in the 1976 best picture nominee, "Network."
Ledger -- who died Jan. 22, 2008 of an accidental prescription drug overdose at age 28 -- won the supporting actor award at the 81st annual Academy Awards ceremony in Los Angeles for his chilling portrayal of the Joker in "The Dark Knight."
Heath's father Kim, sister Kate and mother Sally Bell accepted the Oscar on the actor's behalf.
"This is ever so humbling, just to be amongst such wonderful people in such a wonderful industry," Kim Ledger told the star-studded crowd. "This award tonight would have humbly validated Heath's quiet determination to be truly accepted by you all here -- his peers -- within an industry he so loved."
"We have been truly overwhelmed by the honor and respect being bestowed upon him with this award," added Bell. "Tonight, we are choosing to celebrate and be happy for what he has achieved."
"We proudly accept this award on behalf of your beautiful Matilda," Kate Ledger said, referring to her brother's 3-year-old daughter.