The Champion deal is effective from January 1 and will run through to 2012. The brand will be sold across JJB's network of UK stores and fitness clubs.
JJB chief executive Chris Ronnie said: "JJB is continually looking for brands that can bring real value to our consumers, and in Champion we feel that we have found exactly such a brand. Champion represents all of the true values of real sports and utmost quality, which is quite unique today, and we are really looking forward to working together with them."
Ronnie has targeted for 25% of sales to come via strategic brand partnerships, which are designed to give the retailer more exclusivity, within 18 months. Champion will largely be exploited in men's clothing and will make up a significant amount of the menswear offer.
The agreement will also cover footwear and accessories and JJB will also develop some women's fitness product under the label.
Earlier this year Ronnie signed a similar agreement with Cougar.