{ "background": "Strengthening primary care is a critical component of health systems reform in sub-Saharan Africa. Urban primary care networks (UPCNs) have been implemented in several regions to improve service integration and quality, but rigorous quantitative evidence of their impact on clinical outcomes remains limited.", "purpose and objectives": "This study aimed to quantify the causal effect of a large-scale UPCN initiative on key clinical outcomes for adult patients with hypertension and diabetes in urban Tanzania.", "methodology": "We employed a quasi-experimental difference-in-differences design, analysing longitudinal patient-level data from routine health information systems. The treatment group comprised facilities within the UPCN programme, matched with comparable control facilities. The primary model was specified as: $Y{it} = \\beta0 + \\beta1 (Treati \\times Postt) + \\gammai + \\deltat + \\epsilon{it}$, where $Y_{it}$ is the outcome for facility $i$ at time $t$. Inference was based on cluster-robust standard errors.", "findings": "The UPCN intervention was associated with a statistically significant 12.4 percentage-point increase (95% CI: 8.1, 16.7) in the proportion of patients achieving controlled blood pressure. Improvements in glycaemic control and medication adherence were also observed, though effects were more modest.", "conclusion": "The structured UPCN model significantly improved the management of non-communicable diseases in an urban African setting, demonstrating its potential as an effective health systems intervention.", "recommendations": "Health policymakers should consider the scaled adoption of the UPCN model in similar urban contexts, with parallel investments in health information systems to enable ongoing monitoring and evaluation.", "key words": "primary health care, health systems, non-communicable diseases, quasi-experimental design, programme evaluation, sub-Saharan Africa", "contribution statement": "This study provides novel, causally identified evidence on the clinical effectiveness of an integrated urban primary care