Competing in the 82.5kg weight class at the 1992 Olympic Games in Barcelona, Dimas finished with a lift total of 370 kilograms, as did Krzystof Siemion of Poland and Ibragim Samadov of Unified Team (ex-USSR). Samadov ranked third because he outweighed the other two by five grams, but Dimas and Siemion weighed exactly the same. A new tie-breaking rule awarded the gold medal to whichever lifter reached his final total first. This was Dimas, who gained Greece's first Olympic weightlifting championship since 1904.
After winning two of the next three world championships, Dimas entered the 1996 Olympic Games in Atlanta as the world record holder. He did not disappoint his fans, as he broke the world record in both the snatch and the jerk and defeated Marc Huster of Germany by 9 kilograms. Going for a third Olympic title in 2000, Dimas missed his first two snatch attempts and was only in fourth place midway through the competition. He made up the deficiency in the jerk and, as in 1992, he ended up in a three-way tie, this time with Huster and Georgia's Georgi Asanidze at 390 kilograms. Fortunately, he weighed 16 grams less than Huster and 64 grams less than Asanidze, so he did win his third gold medal.
Dimas returned to the Olympic Games in Athens in 2004 and earned the bronze, after which he signalled his retirement by leaving his shoes on the platform, while the appreciative Greek crowd gave him a standing ovation.