Labour market regulation constrains small and medium-sized enterprises’ (SMEs) ability to minimize redundant labour. However, it is often neglected that many SMEs might circumvent these constraints by accessing a business group’s internal labour market (ILM). In this study, we analyse whether SMEs with ILM access—i.e., with an increasing number of sister group companies in the same subnational region-industry—enjoy a labour productivity premium and whether this potential productivity premium depends on the bargaining power of labour. Because intra-group reallocation of redundant personnel often involves substantial changes in employment conditions, we argue that the value of ILM access might be reduced when the bargaining power of workers is high as they can oppose the reallocation or demand significant compensation. Using a panel of 119,801 European SMEs during 2011–2019 (639,675 firm-year observations), we find that SMEs with ILM access show relatively higher labour productivity. Further, our findings suggest that this productivity premium is higher in those contexts associated with lower labour bargaining power.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11187-023-00780-4.