Private equity firm Advent International has bought a majority stake in Zimmermann from the founding family and Italy's Style Capital, in a deal which sources said values the Australian fashion brand at more than one billion US dollars.

While the financial terms were not disclosed, two people close to the matter said the transaction valued the brand at around 14 times its core profit - meaning around $1.15 billion.

Zimmermann has revenue of some $260 million and a more than 30% core profit margin, the people said.

The investment by Advent will allow Zimmermann to speed up expansion abroad including in Asia and the Middle East, and boost its distribution network, including the digital offer, Advent, Zimmermann and Style Capital said in a joint statement.

Style Capital - an Italian private equity firm that specialises in luxury brands and owns labels such as Twin-Set, Sundek and Golden Goose - and the Zimmermann family will retain a relevant minority stake, they said, adding that the company will continue to be run by its founders and current management.

Founded in Sydney in 1991 by sisters Nicky and Simone Zimmermann, the brand has grown in the last three decades to gain international recognition for its luxury swimwear and sophisticated floral prints reminiscent of still-life painting.

In addition to selling its clothing through some top luxury retailers globally, Zimmermann runs a network of 58 of its own stores in Australia, the United States, the UK, Europe and China. It also operates its own webstore. 

Retail and consumer goods are two of the sectors targeted by Advent, whose company portfolio includes sports clothing maker Lululemon, perfume brands Parfums de Marly and Initio Parfums Privés, beauty retailer Douglas and make-up brands bareMinerals, BUXOM and Laura Mercier.