At St. Albans, Spyridon Mastroyannis rowed and swam on the school's varsity teams for all four years. His high school crew came in 4th at Stotesbury his senior year and was Maryland/DC champion twice in the varsity 8+. He holds a school record in the 200 freestyle relay. As a senior, he captained both squads. He also played four years of football, lettering his junior and senior years. He served as his JV team's captain.

The summer before coming to Yale, Spyridon won US Rowing Nationals in the 8+ and 4+ for TBC. His former high school rival, Marcos Carzolio, is now his teammate on Yale's freshman squad.

Spyridon is currently a freshman in Jonathan Edwards College. He plans on majoring in Biomedical Engineering. Spyridon enjoys sailing and visiting his family in Greece.