The marketing appeal of sport associations extends to sportswear brands, with the result that they are increasingly allied with fashion designer brands. Effects of such alliances are tested experimentally using price and user image as dependent variables. Among males, co-branding with a fashion designer brand generated a higher expected price for shirts bearing the sportswear logo, but adding a sportswear logo did not affect the expected price of shirts bearing a fashion designer logo. Among females, co-branding with a sportswear brand generated a lower expected price for shirts bearing a fashion designer logo, but adding a fashion designer logo did not affect the expected price of shirts bearing a sportswear logo. Both males and females expected the price to be higher when the shirt projected higher engagement or dominance for the wearer. Co-branding can have negative as well as positive effects for partners in a brand alliance.