 He joined AEK in time for the 1963 season for the paltry sum of 140,000 drachmas.Papaioannou proved an instant success helping AEK win their first post-World War II title, scoring twice in the final playoff game of the season against Panathinaikos FC.He with Kostas Nestoridis were one of the best scoring couples in AEK Athens' history and beloved by the fans.