The sports retailer, which has around 400 UK stores and operations in 19 countries in Europe, will open three flagships stores in Australia and one in New Zealand as well as set up an online joint venture.
Sports Direct has cut the deal with MySale unit OzSale.com.au, which will give the sports retailer access to the online group's 12 million members.
This deal comes a month after Sports Direct bought a 4.8% stake in MySale worth around £15 million, which in turn came just two days after the online business floated in London raising £40 million to expand its operations.
The Australian and New Zealand websites will launch later this year, and Sports Direct plans to begin opening its stores 'down under' at around the same time.
Sports Direct chief executive Dave Forsey said: "It will be great to enter these markets, where sport is a way of life."
Sports Direct, also owns a number of brands such as Dunlop, Karrimor and Slazenger. The retailer is controlled by Mike Ashley, who owns 58% of the firm, and also owns Newcastle United Football Club.
MySale is run by Rutland-born brothers Jamie and Carl Jackson who set up the business seven years ago in Sydney.
MySale executive vice chairman Jamie Jackson added: "Sports Direct showed its confidence in our business when it took a 4.8% stake in us a month ago, shortly after our successful initial public offering. This partnership is the logical next step in the development of our relationship."
Retail tycoon Sir Philip Green, who runs Topshop and BHS, also owns just over 22% of MySale.
On Thursday Sport Direct is expected to report underlying earnings up 13.6% to £327.1 million for the year to April 14, on the back of strong organic growth, European acquisitions and rising online sales.