The size and price of the stake were not disclosed. Both groups are privately owned. Analysts have suggested that Geneva-based Martini & Rossi is worth about pounds 1bn.
The deal will create 'a first- class global wine and spirits group with one of the strongest distribution networks and portfolio of brands in the industry,' the two groups said.
Each has annual sales of between dollars 1.5bn and dollars 2bn ( pounds 750m- pounds 1bn). Bacardi rum is the top-selling spirit brand in the world.
Martini & Rossi started considering a restructuring of its own shareholding, including internal and external options, in the spring. When word leaked out, about half a dozen contenders made approaches, reportedly including Allied-Lyons of the UK.
Bacardi was chosen partly because it, too, was a private company and because the groups had worked together for some years.