Worshippers across the country gathered in churches and cathedrals decorated with twinkling lights for the midnight service to celebrate the birth of Jesus Christ.
Persons dressed up as Santa Claus cheered the revellers at several places such as malls, markets and parks.
Christmas trees, bells, gifts and cakes were flooded in the markets where several people wearing Santa Claus' signature cap could be seen enjoying the festive spirit.
"Merry Christmas to all fellow citizens, especially our Christian brothers and sisters. May the festival bring happiness to our families and our shared society," President Ram Nath Kovind said on his official Twitter handle.
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Vice President Venkaiah Naidu also wished all citizens on Christmas.
"It reaffirms our faith in the values of compassion and forgiveness taught by Lord Jesus Christ for the enlightenment of humanity. May this bring peace, harmony and happiness," a post on the Twitter handle of the Vice President said.
As the bells tolled, people thronged the churches -- including the Cathedral Church of The Redemption and Sacred Heart Cathedral.
Delhi Chief Minister Arvind Kejriwal tweeted, "Merry Christmas" and celebrated the festival by attending several Christmas programmes in the capital.
The neighbourhoods of churches reverberated with traditional Christmas carols, with gospel bands enthralling the merry-makers with songs such as 'Jingle Bells', 'Oh Holy Night' and 'Santa Claus Is Coming to Town'.
In Kerala, which has a sizable Christian population, special prayers, midnight masses and low key festivities today marked Christmas as the state witnessed massive devastation and loss of life due to cyclone Ockhi last month.
In his Christmas message, Chief Minister Pinarayi Vijayan urged people to observe the day standing along with those who suffered in the cyclone.
In Goa, which has around 27 per cent Christian population, the peal of the midnight bells in churches and the carols in praise of Lord Jesus ushered in the Christmas festivities.
The capital city Panaji was lit up and the markets gleamed with Christmas trees, bells, gifts, cakes and bebinca (a traditional Goan dessert), as tourists flocked to celebrate the festival in the coastal state.
A larger-than-life crib installed in front of Mary Immaculate Conception Church in Panaji was a major attraction with thousands of tourists visiting the place since midnight.
The streets of Panaji and Margao, the two main cities of Goa, were packed with vehicles till the wee hours as people participated in the traditional dance parties after the prayer service.
The celebrations that commenced today will now continue in the beach state till the New Year.
Archbishop of Goa and Daman, Filipe Neri Ferrao, in his message, appealed to the people to spread the message of peace, love and harmony.
In Chennai, senior bishops and priests conducted special masses at churches and read out the Christmas message at churches across the city.
A large number of people thronged the Annai Velankanni church at Besant Nagar in the city, offered prayers and exchanged greetings.
Faithful from all over the country gathered in large numbers at Shrine Basilica of our Lady of Health in Vailankanni and also New Jerusalem Church at Tarangambadi, the oldest protestant church in Asia, and offered prayers.
The festival mood was also visible in Mumbai. A 65-feet, or as tall as a seven-storey building, pine conifer at a society in Worli attracted visitors, for its tag of being India's tallest fully decorated Christmas tree.
The tree, located at a garden in Adarsh Nagar society in South Mumbai's Worli area, has been decorated with over 10,000 lights, bells, images of reindeer and snowmen, and a waving Santa Claus.
Kolkata celebrated Christmas by holding midnight masses and carols that continued through the day.
The incident was caught in CCTV camera of the Baptist Church at Hawakana area of the town and it had also gone viral on social media with people condemning the incident which took place hours after the midnight service.
In Uttar Pradesh, police kept a strict vigil across the state to ensure Christmas festivities passed off peacefully in the wake of the Hindu Jagran Manch warning against celebrating the festival.
All SPs were put on maximum alert in the districts after the Manch, an RSS-affiliate, recently issued a circular threatening all Aligarh schools against celebrating Christmas saying, they would be doing it "at their own risk".