Abstract Background Health and social service system was reformed in Finland at the beginning of 2023. The responsibility for organizing health and social services was transferred from c. 300 municipalities to 22 well-being services counties (WBSCs). One aim of the reform was to support integration between and within health and social services. The purpose of this study is to describe strategic leadership approaches to implementing integrated care. The study highlights the issues that should be paid attention to when integrated care practices are implemented. Methods The qualitative study utilized semi-structured interviews collected from the upper-level leaders of the WBSCs (n = 25) responsible for the implementation of the reform. The interviewees represented 11 WBSCs. The data were collected in May-August 2023. Inductive content analysis was used for data analysis. Results Four strategic leadership approaches to implementing integration were identified: 1) service user-based leadership approach, 2) partnership-based leadership approach, 3) service system-based leadership approach, and 4) knowledge-based leadership approach. Most of the interviewees combined several different leadership approaches in their talk. Each approach emphasized different aspects of implementing integration and the contextual factors that have to be addressed at different levels of the health and social service system. Conclusions While the macro level reform toward more integrated health and social service system was implemented, the findings reveal that more efforts are required at the meso and micro levels of the system to fulfill the goal of integrated services. The paper highlights the importance of strategic leadership and its different aspects in implementing integrated care at different levels of the system. Key messages • The paper provides a way of comprehending integration from the perspective of strategic leadership. • The conceptualization through the different leadership approaches may facilitate forming a shared vision for integration among leaders and managers.