This study evaluates the economic impact of participation in the Value Chain Development Programme (VCDP) on the net farm income of cassava farmers in Anambra and Enugu States, Nigeria. Utilizing primary survey data from 600 smallholder cassava farmers (334 participants and 266 non-participants), the analysis employs an Augmented Inverse Probability Weighting (AIPW) estimator to control for selection bias and endogeneity, with Propensity Score Matching (PSM) and independent samples t-tests used as robustness checks. The findings show that VCDP participants generated substantially higher total revenue than non-participants (₦2,639,486.78 and ₦1,724,681.80), largely driven by higher yield outputs among participants (33.68 tonnes) compared with non-participants (21.98 tonnes) rather than price differentials. Descriptive analysis reveals an observed mean net farm income of ₦2,223,971 for participants compared to ₦1,409,672 for non-participants. The doubly robust AIPW estimation confirms a positive, statistically significant causal effect, indicating that VCDP participation increased annual net farm income by ₦813,903.30 (p<0.001). Robustness checks using PSM showed a highly consistent treatment effect of ₦805,227.70 (p<0.001). Post-estimation diagnostics confirm that propensity score weighting successfully eliminated covariate imbalances, ensuring reliable counterfactual comparisons. Therefore, the study concluded that integrated value-chain interventions effectively enhance farm profitability and smallholder economic welfare, supporting the expansion of coordinated agricultural support models and recommends strengthening and expanding integrated VCDP support, particularly interventions that improve productivity, timely input access, market linkages, and access to agricultural finance, to sustain and broaden income gains among cassava farmers.