Thousands of Muslims dressed in new clothes thronged the Jama Masjid in the walled city early on Tuesday and offered special prayers (namaz) as Eid-ul-Fitr was celebrated across the capital.
Eid marked the end of the holy month of Ramadan - a period of fasting, prayer and charity.
The words "Allah hoo Akbar" resonated in the narrow lanes of Delhi's old quarters from the loudspeakers of the grand old mosque.
The Shahi Imam of Jama Masjid, Syed Ahmed Bukhari, confirmed on Monday night that Eid would be celebrated on Tuesday. "The sighting of the moon has been confirmed. Id mubarak," he said.
Excitement filled the streets, which have been wearing a festive look throughout the one-month period, as soon as the decision was announced.
Through the day, people will meet friends and relatives, and exchange greetings and gifts.
Eid-ul-Fitr is also a festival of sweets and eats with the markets having an array of traditional delicacies on display. People make seviyan and phirni amongst a host of other preparations at home.
Many Muslims also take to acts of charity on the auspicious occasion of Eid.