On July 4, 2013, Diamantidis renewed his contract with Panathinaikos for another 2 years, at a salary of €1.9 million euros net income per year. On October 30, 2014, Diamantidis became the first player in EuroLeague history to have dished out at least 1,000 career assists. On September 2, 2015, Diamantidis announced his retirement from playing professional club basketball, effective at the end of the 2015–16 Greek League season. In his last season with Panathinaikos, he was voted the Greek League Most Popular Player. Diamantidis retired as the all-time career leader in both assists and Performance Index Rating (PIR) in the entire history of the EuroLeague. Those records were eventually broken.