On 5 January 2015, Aimar returned to River Plate for the club's pre-season training, stating that he would sign with the club only if he could deal with the physical demand after having undergone surgeries to his heel and not having played since leaving Johor Darul in April 2014. On 31 May, he played as substitute in a home win against Rosario Central in the Primera División. Aimar announced his retirement on 14 July 2015 after River Plate coach Marcelo Gallardo informed him that he was not included in the club's squad for the semi-final stage of the Copa Libertadores. Gallardo said Aimar was "suffering" and had struggled with injuries through the pre-season.