The complex nature of Sport for Development (SfD) programmes makes impact evaluation challenging. Realist evaluation has been proposed as a new, theory-driven approach to evaluate complex programmes. The present study aimed to explore the value of conducting realist interviews to gain improved insight into the mechanisms and outcomes of three SfD programmes in the Netherlands: a programme that promotes sports participation among socially vulnerable youth; a combined lifestyle intervention for adults of low social economic status; and a sports-based programme for marginalised adults. In addition, the study aimed to investigate the applicability of a conceptual model from the field of social enterprise (Roy, Baker, & Kerr, 2017) as the preliminary programme theory for those interviews. First, for each programme, a realist interview was conducted with one researcher as the key informant. Thereafter, the findings from and experiences with the individual realist interviews were discussed among the informants in a group meeting. The results revealed that the conceptual model functioned well as preliminary programme theory for the SfD programmes. The realist interviews contributed to theoretical awareness and trustworthiness. Importantly, the interviews highlighted knowledge gaps and generated ideas for programme improvement. Hence, the realist interview technique is recommended as a methodological tool to generate, validate, and improve programme theory in the field of SfD. This study had, however, an explorative character, and more research is needed to confirm and generalize the findings and to learn how a greater number of stakeholders might contribute to this type of realist evaluation.