State media and Assad's official Twitter feed posted photos of the embattled president praying alongside the country's top cleric and members of his government.
"President Bashar al-Assad leads Eid al-Adha prayers at the Nuaman bin Bashir mosque in Damascus," state news agency SANA said.
Adnan Afyouni, Damascus's top cleric, used his sermon to criticise the international community for backing an uprising against Assad that began in 2011.
"Eid is associated with happiness in the life of the Muslim nation," he said.
"But Eid has not entered our homes because the West and its Arab collaborators decided to make our country a battlefield... and implement interests and agendas," he said.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Syria's government has long accused Western and Arab backers of the uprising against Assad of supporting "terrorism" and trying to destroy the country.
"We pledge to God almighty to protect our country from a great conspiracy that targets its role and presence and resilience," he said.
"We pledge to keep the country from being turned into a war zone, torn apart and divided," he said, referring to "plans drawn up at the White House and carried out today in north and east Syria."
The comments appeared to be a reference to strikes by a US-led coalition against the jihadist Islamic State group, which has strongholds in the north and east of the country.
More than 180,000 people have been killed in Syria since the beginning of the uprising against Assad in March 2011.
The country's conflict began with anti-government demonstrations, but spiralled into a vicious civil war after the regime opened fire on protesters.
