Theodoridis started his career at the academies of
AEK Athens and was promoted to the men's team in 1969 with the renewal of roster attempted by the manager,
Branko Stanković. Despite he played mainly as a centre-back, he was good with the ball at his feet and had good positioning, resulting in him being used as a right back, as well. He was a key player in the course of AEK to the
semi-finals of the
UEFA Cup in 1977. With AEK Theodoridis won 2
Greek Championships and a
Greek Cup, including a domestic double in 1978. In the summer of 1978 he moved to
Olympiacos, where he played for one season, before he closing his career at
OFI in 1980. ==International career==