PurposeThis paper explores the drivers and inhibitors of the transition of entrepreneurial family firms from small to large firms. We adopt two contrasting theoretical perspectives, i.e. agency and stewardship, to explore the effects of family power on size transition.Design/methodology/approachWe adopted an original research design that leverages a unique longitudinal database built starting from the list of the 500 best Italian manufacturing family firms published by the AUB Monitor in 2018. Specifically, we tested our hypotheses using a comprehensive set of financial and governance data from 89 Italian manufacturing family firms covering a 10-year period. To test our hypotheses, we conducted a survival analysis using a Cox regression.FindingsWe find an inverted U-shaped relationship between family involvement in ownership and size transition: size transition is more likely to happen at intermediate levels of family involvement in ownership. Additionally, our analysis shows that family involvement in the board of directors negatively impacts size transition, while the presence of a family CEO has a positive influence.Originality/valueTo the best of our knowledge, this study represents the first exploration of the phenomenon of size transition within entrepreneurial family firms. We believe it was worthwhile for two reasons. First, small size is frequently regarded as a weakness when competing in international markets, investing in R&D, or rewarding shareholders. Second, since small family firms are the major contributors to the world economy, understanding the factors that facilitate their transition to large firms can have a significant impact on overall economic development and prosperity.