High-growth firms (HCF) represent a highly desirable subset of firms, which provide disproportionate economic gains, and greater insight into their determinants which is of interest to policymakers, scholars and business owners. We contribute to the literature on HGFs, which is largely absent of cross-national institutional studies, by examining the institutional conditions driving HGFs in 26 transition countries over a long period comprising three panels between 1998 and 2009. Using an institutional hierarchy approach, we test for the influence of formal and informal institutions on HGF prevalence in countries. Our analysis relies first on a principal component analysis to identify institutional factors. Second, we use GLS estimation to test the influence of these three factors on HGF prevalence in a country, followed by a robustness check. Our results show that interaction effects, rather than direct effects, are useful in explaining systematic variations in HGFs prevalence in transition economies. We find that the interaction between formal and informal institutions positively influences HGFs. Further, we find that in fast-reforming transition economies, more burdensome formal institutions discourage HGFs but in slow-reforming transition economies, informal institutions encourage HGFs.