Diarrheal diseases are a significant health concern among urban adolescents in Lagos, Nigeria, with limited access to healthcare and sanitation facilities. A mixed-methods approach was employed, including surveys, focus groups, and observational studies to assess CHW programme impact over two years. CHWs provided significant support with hygiene education (92% of adolescents reported improved handwashing practices) and timely referrals for treatment (78% of cases were successfully referred within a week). Community health worker programmes significantly enhanced adolescent access to healthcare and sanitation, reducing diarrheal disease incidence. Expand CHW training in urban settings and integrate community engagement strategies into existing public health initiatives. Diarrhea Prevention, Community Health Workers, Adolescent Health, Lagos, Nigeria Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.