Paul Stirling claimed the wicket of Kusal Perera for nought on the second ball of the innings and soon Joshua Little took two in two to send back Dinesh Chandimal and Avishka Fernando.
Hasaranga, an allrounder who bowls leg-spin, took the attack to the opposition with four straight boundaries off spinner Simi Singh to lay the foundation for Sri Lanka's challenging total.
He raised his maiden T20 international fifty in 38 balls and kept up the charge to punish the Ireland bowlers, including a towering six before falling to Mark Adair.
Nissanka was equally efficient and also recorded his first fifty in the shortest international format as he hit six fours and one six in his 47-ball knock.
Little returned impressive figures of 4-23 -- his T20 best -- including Nissanka's scalp from his four overs of left-arm pace.
Adair claimed his 50th T20I wicket before Sri Lanka skipper Dasun Shanaka finished the innings with a six and a four in his unbeaten 21 off 11 balls.
Both teams are undefeated after winning their opening games in group A and a victory here will brighten their chances of progressing to the Super 12 stage which starts on Saturday.