Victoria County Court judge Felicity Hampel said Vinod Johnny Kumar, 31, had shamelessly preyed on the women, all of whom were in wheelchairs, had cerebral palsy and required round-the-clock care, the Age reported Thursday.
Kumar, a former casual worker at Yooralla, was charged with raping two women residents and sexually assaulting two other severely disabled residents between October 2011 and February 2012.
Yooralla is the largest non-government disability service provider in Victoria.
"You were employed as a carer for these people whose vulnerability was increased because of the physical and intellectual disabilities they suffered," judge Hampel said.
"They were powerless to defend themselves or to physically remonstrate with you," the judge said.
Judge Hampel said Kumar's action was not opportunistic or spontaneous as he was careful to choose the time and place when committing the offences.
The judge added Kumar made sure that he was the only person on duty when he raped the vulnerable women.
Sanjib Roy, chief executive officer of Yooralla said, the organisation was "greatly distressed that such an incident could occur and we have put extensive measures in place to prevent something of this nature from happening again".
Kumar arrived in Australia from India on a student visa in 2007.