Stephen Doheny top-scored with 84 as Ireland beat Zimbabwe by 46 runs on Saturday.
After losing the toss and being put into bat, Ireland made 294-7 at Harare Sports Club with Doheny and Harry Tector (75) the chief contributors.
In response, Zimbabwe never matched the tourists’ run rate and despite half-centuries from former England Test batsman Gary Ballance (52) and Innocent Kaia (51), they fell short.
Zimbabwe were all out for 248 in 47.3 overs, and now the stage is set for a series decider in the Zimbabwe capital on Monday.
The result bucked a trend as the team winning the toss and opting to bat second won all four previous tour matches – three in a T20I series won 2-1 by Zimbabwe and the first ODI.
Doheny, 24, made his ODI debut in the series opener and scored just three runs as Zimbabwe won by three wickets.
But it was a different story in his second outing as he struck a six and seven fours before being caught at mid-off by Ballance.
Opening partner Paul Stirling, deputising as captain for the injured Andy Balbirnie, set a good example with 45 runs, including two sixes and four fours, before Ballance caught him at fine leg.
Tector followed up a century three days ago with a brisk 75 off 61 deliveries, including one six and seven fours, before he was caught by Ryan Burl at deep mid-wicket.
Tendai Chatara (3-51) and Burl (2-66) were the best of the Zimbabwe bowlers.
Ballance was caught at long-off by Josh Little attempting an off drive having faced 67 balls and hit two fours.
Stirling caught Kaia, who struck a six and three fours, at extra cover off a short delivery from Little (4-38), the most successful Irish bowler.
The Gujarat Titans have hired Little for the IPL season, making him the first Irish international to get an IPL contract.
© Agence France-Presse