Pathirana-inspired Sri Lanka beat Bangladesh in Asia Cup
Spinner Maheesh Theekshana struck early before Pathirana joined forces to dismiss Bangladesh for 164 in the opener of the Sri Lanka leg of the 50-over tournament, a precursor to October's ODI World Cup in India.
Sadeera Samarawickrama, who made 54, and Charith Asalanka, unbeaten on 62, guided the chase in their key stand of 78 after Sri Lanka lost their openers early and slipped to 43-3.
Samarawickrama registered his fourth ODI half-century to raise the noise of the sparse crowd at the scenic venue.
He finally fell stumped off spinner Mahedi Hasan and Shakib Al Hasan soon sent back Dhananjaya de Silva, but the left-handed Asalanka pulled the team home in 39 overs with a winning boundary.
Asalanka reached his 50 in 85 balls to play a patient knock on a pitch where run-scoring did not seem easy. Skipper Dasun Shanaka stood unbeaten on 14.
The bowlers set up victory with Pathirana, whose yorkers have earned him comparisons to Lasith Malinga, picking up key wickets including skipper Shakib and wicketkeeper-batsman Mushfiqur Rahim.
Top-order batsman Najmul Hossain Shanto made 89 to play a lone hand in Bangladesh's innings after they elected to bat first but lasted for only 42.4 overs.
Theekshana struck first when he trapped debutant Tanzid Hasan lbw for nought while De Silva soon sent back fellow opener Mohammad Naim for 16.
Shanto, who bats at number three, stood calm after Bangladesh lost their openers and put on key partnerships including a 59-run fourth-wicket stand with Towhid Hridoy, who was next best with 20.
He registered his fourth ODI half-century and hit seven boundaries but the rest of the batting fell flat.
Pathirana got skipper Shakib caught behind for five with wicketkeeper Kusal Mendis taking a diving catch to his left.
Later he returned to wipe off the tail after Theekshana bowled Shanto with his mystery spin to end the left-hander's 122-ball knock.
Mehidy Hasan Miraz's run-out only added to Bangladesh's woes, after a mix-up with Shanto.
Sri Lanka, who won the T20 edition of the tournament in Dubai last year, are co-hosting with Pakistan and will next play Afghanistan in Lahore.
Pakistan, who won the tournament opener against Nepal, will clash with arch-rivals India in Pallekele on Saturday.