The festival marked the end of Ramadan, the Islamic holy month of fasting.
Greetings of "Eid Mubarak" and "Chaand Mubarak" poured in with the sighting of the thin crescent Shawaal moon Monday evening. West Bengal Chief Minister Mamata Banerjee posted greetings on her official Facebook page.
At the mosque, Muslims hugged one another ignoring class differences. Many of those settled abroad made it a point to return to Kolkata to celebrate Eid with their family members.
The sprawling Red Road in Kolkata saw over 42,000 devotees sitting on rugs and offering prayer.
The mass prayers were followed by day-long merry-making, a large part of which revolves around feasts.
Mughlai cuisine, including varieties of biryanis, kebabs, fresh fruits and home-made desserts, were seen on every platter.
The festival is an all-inclusive affair in Kolkata where people from other faiths also take part in the celebrations.
Fairs and cultural programmes were organised in different pockets of the city where children donning traditional attires were seen revelling in festive spirits.
Women gathered around at henna stalls to adorn themselves with the art while children received money from their elders as gift.
Heavy security arrangements were made across the city and the state to prevent any untoward incident.