At the 2008 Summer Olympics in Beijing, Pastras qualified again for the men's 100 m butterfly by eclipsing a FINA B-standard entry time of 53.45 from the Nioveia Grand Prix in Thessaloniki. He challenged seven other swimmers on the same heat as Athens, including Olympic veterans Juan Veloz of Mexico and Michal Rubáček of the Czech Republic. Pastras cruised to second place by 0.17 of a second behind Denmark's Jakob Andkjær, breaking both his personal best and Greek record of 52.41 seconds. Pastras failed to advance into the semifinals, as he placed twenty-fifth out of 66 swimmers in the preliminaries.