There has been a prominent stream of research investigating internationalisation of organisations. While the importance of transaction costs in the governance decisions of firms has been well established in the literature, transaction cost theory (TCT) in family firms remains underutilised. We examine the impact of family governance (i.e. family ownership and involvement in management and the board of directors) on internationalisation within the domain of TCT using 386 S&P 500 firms. Our findings indicate an inverted U-shaped relationship between family ownership and internationalisation and a U-shaped relationship between family's involvement in management and the board and internationalisation. This illustrates the interesting differential impact of the components of family involvement on internationalisation. We conclude by discussing future research and implications for practice.Keywords: family firms; family management; family ownership; internationalisation; transaction cost theory.Reference to this paper should be made as follows: Memili, E., Misra, K., Chrisman, J.J. and Welsh, D.H.B. (2017) 'Internationalisation of publicly traded family firms: a transaction cost theory perspective and longitudinal analysis', Int.