An ex-nurse who worked at a Victorian hospital while unregistered has been fined 16 times more than his original sentence after an appeal by prosecutors.

Alexis Travero Alvarez, 49, was fined $1000 and placed on a good behaviour bond in May after being found guilty on four charges of working while unregistered.

He was banned from nursing after he pretended to be a migration agent. In June 2019 he pleaded guilty and was convicted for asking for or receiving a fee for giving immigration assistance.

He duped several overseas-trained colleagues out of more than $40,000 between 2013 and 2014.

Alvarez surrendered his nursing registration after the Australian Health Practitioner Regulation Agency told him they would suspend it over the immigration convictions.

Despite this, he worked four shifts at Cabrini Hospital in October 2019 where he was paid and cared for acute cardiac patients.

He administered medications including opioids and then entered an incorrect nursing registration number on his time sheets, the County Court heard on Monday.

In May, magistrate Stephen Lee said Alvarez's personal circumstances mitigated his offending and found he had already been punished by losing his ability to work as a nurse.

Alvarez was placed on a three-year good behaviour bond and ordered to pay the court $1000.

Prosecutors appealed this sentence, arguing the fine was too low given the seriousness and gravity of Alvarez's offending.

Judge Amanda Chambers set aside the Magistrates Court's sentence, instead convicting and fining Alvarez $16,000.

"This was a deliberate act of holding oneself out as a registered nurse when he was not," she told the court on Monday.

"He did have adequate time to desist, this was not one-off offending.

"I'm satisfied he did so knowingly and deliberately against a background as an experienced nurse who'd worked as a registered nurse for many years."