Community health workers (CHWs) play a crucial role in primary healthcare settings, particularly in underserved urban communities where access to mental health services is limited. The study employed a mixed-methods approach, including pre- and post-training assessments with CHWs, focus group discussions, and longitudinal follow-up surveys over two years. Data were analysed using descriptive statistics and thematic analysis. CHWs showed significant improvement in MHFA knowledge scores from baseline to post-training (mean increase of 52%, CI [40-65], p < 0.001), indicating a substantial learning effect. Training CHWs in MHFA demonstrated promising results, enhancing their ability to identify and respond to mental health crises within urban communities. Further research should explore the sustainability of these training programmes and their impact on both CHW practice and community mental health outcomes. Community Health Workers, Mental Health First Aid, Urban Settings, Training Effectiveness Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.