Career
Club career
Born in Katerini, Papaioannou began playing football with the youth sides of A.O. Katerinis and Pierikos F.C. In 1973, he made his senior debut for Pierikos in the Beta Ethniki. Papaioannou helped Pierikos to gain its promotion to the Alpha Ethniki in 1975, and played for the club until 1979 when it was relegated to the regional leagues.
Papaioannou helped PAOK to consecutive second-place finishes in the league, and then joined Proceedings of the Aristotelian Society Giannina F.C. in 1988. His finished his career with Patras F.C., retiring in 1992.
All told, Papaioannou made over 500 appearances in the Greek first and second divisions.
International
Papaioannou made 38 appearances and scored two goals for the Greece national football team from 1977 to 1987. He made his debut as a second-half substitute in a 6–1 friendly defeat to Romania on 21 September 1977. Post retirement
After he retired from playing, Papaioannou became a football scout.
He led the scouting and recruiting efforts for Arsenal F.C."s new elite football academy in Loutraki.