The tourists bowled Zimbabwe out for 154 before chasing their target inside 25 overs to claim a bonus-point victory.
Four days after Sri Lanka sealed a 2-0 Test series sweep, the tourists bowled Zimbabwe out for 154 before chasing their target inside 25 overs to claim a bonus-point victory.
As with the Test matches, Zimbabwe suffered from the fragility of their top order, falling to 14 for three in the first five overs.
However, this time around they could at least point to some challenging conditions -- Harare experienced heavy rain over the weekend, and cloudy skies on Monday morning gave Sri Lanka?s seamers plenty to work with.
"In losing the toss we knew it was going to be tough, but there were too many soft wickets," said Zimbabwe captain Graeme Cremer. "This was not a 150-type of wicket."
The collapse began in just the fourth over, when Suranga Lakmal had both Brian Chari and Craig Ervine caught at second slip in the space of three deliveries, and in the next over Sikandar Raza Butt's careless legside flick off Nuwan Kulasekara found midwicket.
Sean Williams was then bamboozled by Sachith Pathirana's left-arm spin and was stumped by Niroshen Dickwella, before Nuwan Pradeep dismissed Chamu Chibhabha and Elton Chigumbura in successive overs to leave Zimbabwe 50 for six in the 18th over.
As in the Test series, it was left to Zimbabwe's lower order to repair the damage.
Wicketkeeper-batsman Peter Moor struck a polished 47 and added 55 for the seventh wicket with Graeme Cremer, and once Moor was trapped lbw by Nuwan Kulasekara, Cremer marshalled the tail to good effect.
The Zimbabwe captain put on 31 for the eighth wicket with Donald Tiripano, who made 19, and was left stranded on 31 not out when No. 11 Tinashe Panyangara attempted one big shot too many.
Panyangara sliced a delivery off Asela Gunaratne to cover to give the allrounder figures of 3 for 21 in 6.3 overs, while Kulasekara, Lakmal and Pradeep finished with two wickets apiece as Zimbabwe were bowled out in 41.3 overs.
"Everyone did really well," said Sri Lanka captain Upul Tharanga. "The bowlers stuck to the plan and bowled in the right areas. They knew the wicket would do something."
With Dhananjaya de Silva and Kusal Perera putting on 56 for the first wicket, the result was never in doubt.
Although Perera was well caught at deep square leg by Sikandar Raza for 21 and Niroshan Dickwella fell for 41 with the target in sight, De Silva finished unbeaten on 78 as Sri Lanka romped home in 24.3 overs.
The triangular series also includes the West Indies, who will take on Sri Lanka at the same venue on Wednesday.