PurposeThis study attempts to examine the performance differences between firms with and without integrated management systems (IMSs), and the impact of three integration strategies (i.e. implementing quality management system (QMS) first, then environmental management system (EMS) (QMS + EMS); implementing EMS first, then QMS (EMS + QMS); implementing QMS and EMS simultaneously (QMS − EMS)) on firm performance to reveal the IMS–performance relationship and provide empirical evidence.Design/methodology/approachTwo panel datasets were collected during 2009–2019. This study used the Mann–Whitney non-parametric test and a sample of 33,155 observations from 4,316 Chinese listed firms to compare the performance differences between the IMS and non-IMS groups through performance indicators. This study also examined the effects of three integration strategies on firm performance using a cross-sectional time-series feasible generalized least squares (FGLS) regression model and a sample of 11,289 observations from 2,037 firms.FindingsThe results show that significant performance differences exist between IMS and non-IMS firms; however, the performance of firms with an IMS is not always better than that of firms without IMS. Furthermore, the simultaneous integration strategy has a positive impact, whereas sequential integration strategies (QMS + EMS and EMS + QMS) negatively affect firm performance. Compared with the EMS + QMS strategies, the QMS + EMS strategies have a more prominent effect on firm performance. Simultaneous strategies are more effective than sequential strategies.Practical implicationsFirms should fully consider the potential benefits and costs associated with the difficulties of IMS implementation and the implementation order of different management systems and the potential effects of the management systems in different conditions. Firms also should try to develop internal capabilities through implementing different integration strategies.Originality/valueBy comparing performance differences between firms with and without IMS, this study enriches the understanding of the performance benefits of IMS implementation in the Chinese context. By examining the impact of integration strategies that follow different sequences on firm performance, this study promotes an in-depth understanding of the integration strategies and their performance implications beyond simple descriptions and also provides new insights into operations strategy models.