Retail co-branding is an increasingly popular form of growth in mature business format franchises. This paper presents a study of franchised retail co-branding arrangements in Australia utilising a grounded theoretic approach building on previous case study research. Co-branding, agent theoretic and resource constraint arguments are analysed and found to be inadequate when applied to this phenomenon. The research reveals that the motivations for the development of internal co-brands into existing franchises include alignment of a suitable brand with existing retail formats and risk-averse behaviour. This research shows that co-brands are successfully created internally when franchisors are willing to modify the culture and concept of the original franchise brand in order to achieve system growth.