Mantzouranis qualified for the Greek squad in two track cycling events at the 2008 Summer Olympics in Beijing by receiving a berth for his team based on the nation's selection process from the UCI Track World Rankings. Teaming with Vasileios Reppas and Panagiotis Voukelatos in the men's sprint race, held on the first day of track cycling, Mantzouranis recorded a time of 45.645 and a speed of 59.152 km/h to deliver the Greek trio a tenth-place finish in the prelims. The following day, in men's keirin, Mantzouranis missed a chance to advance further to the later rounds, after finishing fifth in the opening prelims, third in the repechage, and seventeenth overall from the final standings.