Sandro Terzini, 48, pleaded guilty on Tuesday to theft of the 1970 Ferrari Daytona Coupe in 2013 from his friend of 20 years.
The County Court was told Terzini's mate asked the motor mechanic to securely store the luxury car at his business, Terzini Motore, which restored and traded exotic cars.
But while the owner was overseas, Terzini went behind his back and sold it for $450,000, without telling him.
It was only 16 months later that the owner - who had still been paying insurance premiums for the vehicle - learned it had been sold.
Crown prosecutor Jonathan Manning said the owner initially asked Terzini to store the car at his Brighton business - after buying it from the UK for 150,000 pounds - as he had done with previous vehicles.
Four years later, he asked Terzini to find potential buyers for it.
But the owner had a change of heart and told Terzini he no longer wanted to sell the Italian marque, days before Terzini sold the vehicle for $450,000 without his consent, transferring $400,000 from his business to personal bank account.
The car has changed hands a further four times and is now in the UK, the court was told.
Mr Manning said the value of the theft and the deceit was significant.
"He obviously didn't tell the victim what had happened," the prosecutor said.
Defence barrister Samuel Tovey said at the time of the theft, his client's life was spiralling downwards, with large debts, a marriage break up and heavy cocaine use.
He argued it wasn't a crime motivated purely by greed and said it stood no chance of remaining undiscovered.
But Judge Rachelle Lewitan countered: "It's a gross breach of trust, isn't it?"
Terzini will be sentenced at a date to be fixed.
