Five defendants were sentenced to 200 years each, five to 220 years, four to 240 years each and one to 260 years, based on their involvement in conspiring and aiding the attacks - meaning they will spend the rest of their lives behind bars.
Nine others accused in the case were acquitted and discharged.
The April 21 attacks targeted three churches and three hotels across the island nation during Easter services and celebrations. They also wounded 574 people.
The bombings, which were inspired by the Islamic State group, were among the deadliest attacks in Sri Lanka's history.
They killed 42 foreigners and devastated communities across the country.
Australian woman Manik Suriaaratchi and her daughter, Alexendria, were among those who died when a bomb exploded inside a church in Negombo, north of the capital, Colombo.
A three-judge bench of judges of the High Court delivered the judgement against 24 suspects after a lengthy trial where the accused faced some 23,000 charges including conspiracy or aiding and abetting to carry out the attack.
Some 2300 witnesses were listed in the case which was heard over 250 days.
Among those sentenced was Mohamed Naufer (Naufer Moulavi), an Islamic cleric with extremist idea who was accused as a mastermind of the Easter Sunday attacks and several relatives of the suicide bombers.
The head of the Catholic Church in Sri Lanka , Cardinal Malcolm Ranjith, was among those who brought pressure on the government to expedite the court proceedings to bring justice to the families.
with AP
