The activists detained were 18-year-old Tibetan student Tsela Zoksang and 22-year-old Joey Siu, a US citizen exiled from Hong Kong.
Greek police, with several dozen officers present, were quick to stop the activists.
The Chinese capital will become the first city to host both the Winter and Summer Games when it stages the event but, as was the case with the 2008 Beijing Olympics, protests and calls for boycotts over the country’s human rights record have marred the run-up.
Chinese authorities have been accused of facilitating forced labor by detaining around a million Uyghurs and other primarily Muslim minorities in camps since 2016.
China denies wrongdoing, saying it has set up vocational training centers to combat extremism.
Sunday’s dress rehearsal at the ancient stadium of Olympia was hampered by brief spells of rain and heavy clouds, with the torch not being lit by the sun’s rays through a parabolic mirror.
Instead, a backup flame from previous rehearsals was used by an actress playing the high priestess.
More rain is expected on Monday, with human rights activists pledging more actions until Tuesday’s flame handover to Chinese Games organizers in Athens.
The Beijing 2008 Summer Games flame ceremony was also severely disrupted by a string of protests from human rights activists, which was the start of international demonstrations over China’s human rights record leading up to the Olympics.