Line managers have an important role in leading implementation of evidence-based practice (EBP). In this task, they are highly influenced by their context. However, little is known about how contextual factors impact managers’ implementation leadership. The aim of the present study is to explore how contextual factors influence line managers’ leadership when implementing EBP. Twenty-eight semi-structured interviews were performed with line managers in social care. A hybrid thematic analysis was carried out. The Consolidated Framework for Implementation Research Framework (CFIR) was used to guide the deductive analysis approach. Findings showed that contextual factors in all of CFIR’s inner setting constructs and in two constructs of the outer-setting domain (Cosmopolitanism and External resources and funding) had a high practical impact on managers’ implementation leadership. However, many of the contextual factors were either not offered to or did not actually reach the managers, which means that they had a limited impact in practice. Moreover, several factors only had a positive practical impact in interaction with other factors, rather than independently. Future research should systematically consider interactions between contextual factors. Identifying factors that have a potential impact in practice may help inform support initiatives to aid managers in developing their implementation leadership.