After Michael Clarke had scored 82 from 81 balls and Shane Watson 81 from 89 in Australia's 290 for seven, Zimbabwe reached 184 for seven to give Australia victory by 106 runs in the 13-a-side match.
The Australians struggled to find their timing on a docile pitch which gave nothing to the faster bowlers.
They reached 91 for no wicket but the middle-order then faltered with captain Ricky Ponting (2), Brad Hodge (17), Mike Hussey (15) and Brad Hogg (5) departing in quick succession.
Clarke, who missed the 3-0 series defeat to New Zealand last month after injuring his hip, looked in fine touch, driving the ball crisply on both sides of the wicket.
When Australia took the field, Shaun Tait was quick but erratic, opening the innings with two consecutive wides, while the rest of the Australia pace bowlers were economical but unpenetrative.
Australia fielded only 12 men with opener Matthew Hayden and all-rounder Andrew Symonds still recovering from injuries.
Wicketkeeper Adam Gilchrist was not considered for selection after delaying his arrival to the Caribbean until Monday because of the birth of his third child. He is scheduled to return to the side for Friday's match against England.
