The dissolution ordered by by President Gotabaya Rajapaksa came six months before the parliamentary term was scheduled to end and his decree said elections will be held on April 25.
Rajapaksa was elected to office last November but has said he cannot work freely because his powers had been reduced. He has also faced restrictions because the opposition commanded a majority in the 225-member Parliament.
The election campaigning period will include the first anniversary of a series of Islamic State-inspired suicide bombings on Easter Sunday last year that killed more than 250 people last year in churches and tourist hotels.
Rajapaksa rode to power criticizing the previous government for serious security and intelligence lapses that preceded way the bombings. It was the worst violence in Sri Lanka since the country's 26-year civil war ended in May 2009.
Constitutional changes initiated by Rajapaksa's predecessor, Maithripala Sirisena, reduced presidential powers, giving them to the Parliament and to independent commissions.
The change virtually created two political power centers — the president and the prime minister, with the prime minister in charge of Parliament and government ministers.
Rajapaksa's brother, former President Mahinda Rajapaksa, is the prime minister and leads a minority government.
Rajapaksa needs two-thirds parliamentary support to pass any changes to the constitution.