After undergoing a 2018–19 season-ending right ankle surgery, for a peroneal tendon rupture, on 1 April 2019, Spanoulis began individual workouts again on 5 July 2019. After his return to individual training, Spanoulis signed a one-year contract extension with Olympiacos, at a salary of €600,000 net income. On 29 November 2019, Spanoulis passed Juan Carlos Navarro, to become the EuroLeague's all-time career leader in Performance Index Rating (PIR). He accomplished the milestone in a EuroLeague 2019–20 season game versus the Italian club Olimpia Milano.