As officials launch a new initiative to speed up slow-moving reconstruction work, President Mahinda Rajapakse will lead commemorative ceremonies with an address in the southern village of Peraliya.
More than 1000 passengers perished in Peraliya when their train was smashed by the giant waves.
Anura Priyadharshana Yapa, media minister, said: "We hope everyone will observe the silence to remember those who died in the tsunami."
The planned ceremonies have been marred by fears of Tamil separatist attacks, and organisers said security had been stepped up for the president's visit.
Reconstruction efforts have been moving slowly, with the government on Saturday admitting that only one fifth of homes damaged - 20,000 of 98,525 - have been rebuilt.
Sri Lanka marks the first anniversary of the tsunami with officials still unable to reconcile tolls from different state agencies.
The numbers vary from 17,500 to 41,000 deaths.
Indian tsunami orphans in a
state-run orphanage centre
The loss of infrastructure was estimated at $900 million and the country's total reconstruction and rehabilitation needs were placed at $2.2 billion.
The government said it received $3.2 billion in aid pledges from international donors.
India also offered tributes on Monday to the thousands killed in last year's tsunami with countrywide memorial services, silent marches and beachside ceremonies.
On the palm-fringed island of Car Nicobar, badly battered by the 26 December 2004 tragedy, India's military unveiled a memorial, while thousands of civilian survivors, mostly Nicobarese tribespeople, left their homes early to remember those washed away within seconds when the giant waves struck.
India lost more than 16,000 people as villages were wiped out along its southern coast and on the Andaman and Nicobar island chain, and suffered material damage estimated by the UN at $2.5 billion.