The move sees Sainsbury re-united with Mark van Bommel, who was the assistant coach with the Socceroos whilre they played at the World Cup in Russia this summer, but has now taken the reigns of PSV in his native Netherlands.
The 26 year-old was on the radar of the likes of QPR and Aston Villa in the Championship in England, but opted to make the move to the Netherlands.
He was previously at Chinese club Jiangsu Suning where he fell out of favour after a positive first season with the club.
Sainsbury spent time on loan at Swiss team Grasshoppers last season before going to the World Cup, where he played in each of the 'Socceroos' 3 games.
The relationship that he struck up with van Bommel while with the Australian national team was one of the key reasons that the defender decided to swap China for northern Europe.
“I am looking forward to working under him again. He has ideas in training and he won't back down from them and that is what all successful coaches do.
“PSV is on another level, everyone knows them in the world and it's a Champions League club, why would you not want to come here?,” the Australian said.