John Stewart McArthur (62) pleaded guilty to receiving before his sentencing at the Dunedin District Court last week.
He claimed he was contacted last year by a woman calling herself "Lisa'', who informed him a sum of money would arrive in his account.
She had rung a bank call centre impersonating a 75-year-old customer and provided enough information to set up an online-banking account.
With unfettered access to the victim's funds, $51,500 was transferred to McArthur's account over two weeks in September last year.
As instructed, the defendant spent $13,000 of the stolen cash on iTunes cards, the numbers of which he would then pass on to "Lisa''.
The rest was spent within the fortnight by McArthur and his girlfriend on "their own pleasures'', Judge Michael Turner said.
The court heard the victim had been so financially crippled by the scam that she needed her grandson to buy groceries for her.
She blamed herself, the judge said, despite doing nothing wrong.
"All caused by you. All caused by greed,'' he told McArthur.
When the woman found her funds bled dry she informed the bank and it froze the defendant's accounts.
McArthur went into the bank and lied to an investigator.
He said the victim - whom he knew by name - was his aunt, sending him trust-fund money that he was entitled to.
His story fell apart when police became involved.
Defence counsel Sophia Thorburn said her client was unaware the money being siphoned through his account was the result of a scam.
There was "sophistication and planning behind the scenes'', Judge Turner said, and he believed McArthur had greater involvement than he claimed.
The bank refunded the victim's money and was now going after the defendant for the stolen sum.
But the court heard he had nothing to show for the spending spree and bankruptcy proceedings were under way.
Ms Thorburn said McArthur had given two phone numbers to the police so they could investigate the identity of "Lisa'', but she understood the inquiry was taken no further.
While the 19-month prison sentence fell within the range for home detention to be considered, the judge said it would not appropriately reflect the offending, given the defendant's significant criminal history.
