After Ireland had been dismissed for 114 in 19.2 overs, a four from wicketkeeper Clive Madande lifted Zimbabwe to 118-5 with 12 balls to spare in the first of a three-match T20 series.
Ballance was born in Harare, making him eligible to switch international allegiance after playing 23 Tests and 16 ODIs in an England career that ended six years ago.
Featuring in his first T20 international, Ballance compiled the second highest Zimbabwe score behind Sean Williams (34) after facing 29 balls and hitting one six and two fours.
His innings ended in the 12th over when a faint nick was caught by wicketkeeper Stephen Doheny off right-arm fast medium bowler Mark Adair.
Man of the match Ryan Burl, who took three wickets for Zimbabwe, hailed Ballance.
"He is a very experienced player and has a calming presence," said leg-spinner Burl.
"He has fitted in well. We are picking his brains, and he is learning from us. We are really happy to have him in the side."
Ballance was released by English county Yorkshire last year after admitting he used racist language against teammate Azeem Rafiq.
Revelations by Pakistan-born Rafiq of institutional racism triggered wholesale changes at the club.
A Zimbabwe Cricket spokesman told reporters that the 33-year-old Ballance was "not yet ready for interviews as he was still settling in".
Zimbabwe lacked star batter Sikandar Raza -- shortlisted for three 2022 International Cricket Council awards -- who is playing franchise cricket in Bangladesh.
Williams carried on where Ballance left off to ensure a home victory in the first of three T20 internationals. The others are scheduled for Saturday and Sunday.
In a 47-minute stand, Williams averaged just over a run a ball and his total included three fours.
Adair and off-spinner Harry Tector were the most successful Irish bowlers, capturing two wickets each.
Put in to bat after Zimbabwe captain Craig Ervine won the toss, Ireland lost openers Ross Adair and skipper Andy Balbirnie with just 12 runs on the scoreboard.
Only Gareth Delany, who top scored with 24, Curtis Campher and Doheny reached double figures while Burl (3-29) was the most successful Zimbabwe bowler.
