Born in Katerini, Papaioannou began playing football with the youth sides of A.O.
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.
[2] Papaioannou helped PAOK to consecutive second-place finishes in the league, and then joined PAS Giannina F.C.
[1] Papaioannou made 38 appearances and scored two goals for the Greece national football team from 1977 to 1987.
[3] He made his debut as a second-half substitute in a 6–1 friendly defeat to Romania on 21 September 1977.