When he finally encountered the Chinese leader and was presented to other dignitaries, observers spotted him appearing to make an odd gesture with his hands, although it remained unclear what he was attempting to communicate.
"I use the same gesture," another user commented.
"It means something is 'so-so' (something normal)."
It's nearly impossible to determine what Putin was genuinely conveying to the Chinese officials, but it appeared good-natured.
Indeed, some observers felt that Putin seemed in such high spirits that he may have been drinking beforehand.
"Anyone else think he seems drunk?" one person questioned online, receiving a flood of agreement from others.
China's President Xi Jinping personally received several leaders at the summit, including Putin, Indian Prime Minister Narendra Modi, and Turkish President Recep Tayyip Erdogan.
Xi is anticipated to conduct discussions with Putin later this week.
The SCO represents a regional security organisation, established to restrict the influence of western alliances such as NATO.
This weekend's gathering was designed to challenge western influence in international affairs.
