Military forces and police armed with assault rifles patrolled the streets leading to churches and stood guard outside the compounds.
Everyone entering was required to produce identity cards and be body searched.
Volunteers were stationed at the gates of churches to identify parishioners and look out for any suspicious individuals.
Parking was banned near the churches and officials urged worshippers to bring only minimum baggage.
Seven suicide bombers struck two Catholic and one Protestant church and three luxury hotels in the attacks last month.
The Islamic State group claimed responsibility for the bombings, which were carried out by a local radicalised Muslim group.
Sunday services were cancelled in the two subsequent weekends amid fears of more attacks, leaving the faithful to hear Mass via live TV transmission from the Colombo residence of Archbishop Malcolm Ranjith.
Church authorities are also considering the reopening of church-run schools on Tuesday if they can be satisfied with security.
President Maithripala Sirisena said last week that "99 per cent" of the remaining suspects in the Easter attacks have been arrested and their explosive materials seized, and it is safe for tourists to return to the Indian Ocean island nation.
Police say two previously little-known radical Islamist groups - National Towheed Jamaat and Jammiyathul Millathu Ibrahim - conspired in the attacks.
Officials say Zahran Hashim, a vitriolic preacher from the country's east, may have led the attackers and was one of the bombers to die.
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