An increasing consensus exists in the impact evaluation literature on using detailed theory-based evaluations to evaluate complex programmes such as private sector development (PSD) programmes. At the same time, PSD managers expect periodic and timely (so-called ‘real-time’) input from evaluators to improve programmes throughout their implementation. This article presents insights from real-time theory-based monitoring and evaluation shaped by the needs of policymakers in two Dutch PSD programmes. To learn about their experiences, we held in-depth interviews with researchers and policymakers involved in the evaluation. The interviews indicated that theorybased evaluation improved reporting on the programmes’ contribution to higher-level impact areas and credibly quantified the importance of that contribution. The insights showed too that real-time monitoring and evaluation of PSD programmes requires more flexibility in data collection and increased interaction with mid-management.