Based on the resource-based view (RBV) theory, this study examines the association between buying firms’ cross functional integration, buyer-supplier integration and supplier logistics performance in buyer-supplier relationships. RBV considers these two organisational dimensions of supply chain integration as strategic resources which play an important role in improving logistics performance. This research examines the effects of both intra-firm integration and inter-firm integration on supplier logistics performance with survey data from key informants in the public medicine supply system in Mainland, Tanzania. The unit of analysis is the purchasing relationships between public health facilities and focal suppliers acting as public agents of the national medical stores department (MSD). The empirical analysis is based on data reported by 166 purchasing managers, and demonstrates that stronger buyer-supplier integration improves supplier logistics performance significantly. There is no main effect of the buying firm’s cross functional integration on supplier logistics performance, but more extensive cross functional integration in the buying firms enforces the effect of buyer-supplier integration on supplier logistics performance significantly, and these findings indicate that extensive cross functional integration in the buying firms provides an administrative infrastructure that enhance the effectivity of extensive supplier-buyer integration.