The High Court in Colombo handed down the sentences on Tuesday after a five-year trial, meaning the convicted men will spend the rest of their lives in prison. The three-judge bench found the group guilty on charges including murder, conspiracy to commit terrorism and possessing firearms, covering more than 23,000 individual offences.
Prosecutors said Naufer Moulavi masterminded the attacks, which were inspired by the Islamic State (IS) group. All the suicide bombers who carried out the blasts died in the attacks. Investigators had previously blamed Islamist extremists for the Easter Sunday bombings.
Among the dead were 45 foreigners, including Australian mother Manik Suriaaratchi and her daughter Alexandria, who were killed when a bomb exploded inside a church in Negombo, north of Colombo.
The trial heard evidence from more than 2,300 witnesses, and prosecutors presented 2,076 pieces of evidence including explosives, swords and firearms. One of the 25 originally indicted men died in custody.
In the wake of the attacks, Sri Lankan authorities acknowledged a "major intelligence lapse" after a tip-off from Indian intelligence about a possible suicide attack was not properly shared. The Supreme Court in 2023 ordered former president Maithripala Sirisena to pay compensation to victims, finding him responsible for national security failures.
Last month, former police chief Pujith Jayasundara and former defence ministry secretary Hemasiri Fernando were sentenced to death for criminal negligence that led to the bombings. However, Sri Lanka has not carried out an execution since 1976 due to a long-standing moratorium, and both are expected to serve life sentences instead.
President Anura Kumara Dissanayake, elected two years ago, had pledged to hold those responsible to account. The sentencing marks a significant milestone for victims' families who have held regular demonstrations demanding justice for the attacks.