[5] Theoklitos began his football journey through the junior ranks at now defunct East Richmond Jaguars.

He was then picked up by South Melbourne FC but failed to make an impact ahead of number 1 Eugene Galekovic.

In the 2006/07 A-League season, Theoklitos kept ten clean sheets from 21 games, attracting interest from both the Australia and Greece national associations.

In early July 2009, he signed a two-year contract with English League One side Norwich City.

[7] In the opening match of the season on 8 August 2009, Theoklitos made his debut for Norwich against Colchester United at Carrow Road, conceding five goals before half-time and seven in total.

[8] However, Gunn did not have the support of the Norwich board, and was replaced by Colchester manager Paul Lambert, who had engineered the 7–1 defeat.

Theo returned after the January Asian Cup break with a 3–2 home win against the Wellington Phoenix, despite conceding a foolish goal which was credited to Kenny Cunningham.

Theo went on to play 3 more matches that season, keeping a clean sheet against the Central Coast Mariners, before injuring his quad muscle.

The Michael Theo Soccer Academy was established in 2010, running annual clinics during the July school holiday period.