Chasing a target of 174, Zimbabwe required 20 runs off the last over bowled by Angelo Mathews, triumphing by winning by four wickets.
Mathews, Sri Lanka's hero with the bat with an unbeaten 66, failed to live up to expectations as Zimbabwe knocked off the target with a ball to spare.
Zimbabwe's Luke Jongwe, who smashed 25 off 12 balls with two fours and two sixes was named man of the match.
He had also claimed two wickets with the ball, but it was his punchy big hitting in the nail-biting last over that took Zimbabwe over the line.
Jongwe smashed the first ball of the final over for six over long-on -- and Mathews had overstepped as well, so the equation came down to 13 off six balls.
Next, Jongwe managed a boundary off the free hit, before smashing a six off the next delivery -- making it three runs required off four balls.
Mathews managed a dot ball next. Then, to make matters worse, Jongwe was dropped off the next delivery and the batters completed a single.
Clive Madande was on strike for the penultimate ball, and as Mathews missed the yorker, he swept it for six to finish the match in style.
Sri Lanka were sloppy in the field, dropping a couple of catches, and there were a few misfields as well.
It was opening batsman Craig Ervine who kept Zimbabwe in the hunt, top scoring with 70 runs off 54 balls with six fours and two sixes.
It was Ervine's career best T20 score.
The spinners were Sri Lanka's trump card and Ervine tackled them well, playing the sweep and the reverse sweep to good effect and upsetting their rhythm.
Sri Lanka got off to a poor start as they were 27 for four but a 118-run stand between Mathews and Charith Asalanka bailed them out.
It was a record fifth-wicket partnership for Sri Lanka, improving on the 86-run stand between Asalanka and Bhanuka Rajapaksa against Bangladesh in Sharjah in 2021.
Mathews posted his sixth half-century in T20 cricket and was unbeaten on 66, while Asalanka hammered his fifth half-century and top scored with 69.
But their efforts proved to be futile as Zimbabwe pulled off an unlikely win.
Sri Lanka had won the first game on Sunday and Thursday's final game will be the series decider.
© 2024 AFP