Abstract Background Results-Based Financing (RBF) has proliferated in the health sectors of low and middle income countries, especially those which are fragile or conflict-affected, and has been presented by some as a way of reforming and strengthening strategic purchasing. However, few if any studies have empirically and systematically examined how RBF impacts on health care purchasing. This article examines this question in the context of Zimbabwe’s national RBF programme. Methods The article is based on a documentary review, including 60 documents from 2008 to 2018, and 40 key informant (KI) interviews conducted with international, national and district level stakeholders in early 2018 in Zimbabwe. Interviews and analysis of both datasets followed an existing framework for strategic purchasing, adapted to reflect changes over. Results We find that some functions, such as assessing service infrastructure gaps, are unaffected by RBF, while others, such as mobilising resources, are partially affected, as RBF has focused on one package of care (maternal and child health services) within the wider essential health care, and has contributed important but marginal costs. Overall purchasing arrangements remain fragmented. Limited improvements have been made to community engagement. The clearest changes to purchasing arrangements relate to providers, at least in relation to the RBF services. Its achievements included enabling flexible resources to reach primary providers, funding supervision and emphasising the importance of reporting. Conclusions Our analysis suggests that RBF in Zimbabwe, at least at this early stage, is mainly functioning as an additional source of funding and as a provider payment mechanism, focussed on the primary care level for MCH services. RBF in this case brought focus to specific outputs but remained one provider payment mechanism amongst many, with limited traction over the main service delivery inputs and programmes. Zimbabwe’s economic and political crisis provided an important entry point for RBF, but Zimbabwe did not present a ‘blank slate’ for RBF to reform: it was a functional health system pre-crisis, which enabled relatively swift scale-up of RBF but also meant that the potential for restructuring of institutional purchasing relationships was limited. This highlights the need for realistic and contextually tailored expectations of RBF.