They held placards condemning the attacks.
The protesters voiced strong opposition to any possible dispatch of South Korean troops to what they called a "war of aggression."
Participants carried signs that read "No troop dispatch in the war of aggression!"
This demonstration reflects growing public and political concern in South Korea over the ongoing conflict in the Middle East.
Similar protests have taken place in recent weeks.
Buddhist monks from the Jogye Order marched toward the US Embassy while performing full-body prostrations to protest the strikes and any warship deployment to the Strait of Hormuz.
South Korean officials have stated that Seoul has not received any official request from the United States to send forces to the region.
The protests come amid heightened regional tensions following the US-Israeli military aggression against Iran that began in late February 2026.