© The Author(s) 2020. The dynamics of employment relations in small and medium-sized enterprises (SMEs) have attracted academic interest since the 1970s. To date, research debates have converged around two competing perspectives extolling either the opportunities, or the exploitation caused by informal working practices in smaller sized firms. Responding to calls for a more balanced and nuanced view, we analyse n = 1764 responses from a nationally representative study of workplace relations in Ireland, specifically focusing on negative behaviours in SMEs. We contribute to bullying and SME literatures by disaggregating the SME label and showing that certain employee groups in medium-sized firms are likely to report higher incidences of ill-treatment than their counterparts in smaller and larger firms. We conclude by making recommendations on how managers, owners and HRM practitioners can use our study¿s findings to improve employee experiences and tackle bullying, harassment and other types of ill-treatment in their respective working environments.