Hayden Charles Ledger pleaded not guilty to receiving $130,000 (£81,250) worth of stolen machinery in 2008.
The charge carries a maximum penalty of two years jail or a fine of up to $20,880 (£13,050) in Australia's Midland Magistrates Court.
According to Sky News Australia, Ledger's lawyer appealed for a more lenient charge because his client suffers from bipolar disorder.
Ledger reportedly attempted to get out of a jail sentence by arguing he was distraught by the actor's death from a prescription drug overdose, and should not be held responsible for his crime.
But the judge ignored his plea for leniency and sentenced him to 18 months in jail.