Afghanistan beat Ireland by 22 runs, leaving the Irish leading their Twenty20 series 2-1 with two more matches to play at Stormont next week.
A half-century by Rahmanullah Gurbaz helped the tourists to 189-5.
Ireland struggled from the off in their reply as they lost openers Paul Stirling for a duck and Andrew Balbirnie for one to lie 19-2.
Wickets continued to fall steadily and despite a late unbeaten 58 from George Dockrell, they fell short with 167-9.
Ireland had won the first two matches at the Belfast venue and retain a slender lead going into the final two encounters on Monday and Wednesday.
The Irish were struggling badly at 85-7 in the 13th over when Dockrell and debutant Fionn Hand (36) teamed up to put on 74 for the eighth wicket, the former hitting two sixes and six fours.
Ultimately, the home side never looked likely to reach their target and their opponents ran out deserved victors.