Traditional African vegetables have recently received considerable attention for their contribution to food and nutrition security and opportunities for enhancing smallholder livelihoods. Promoting the production and consumption of traditional vegetables is expected to enhance household nutrition among urban and rural households. The Good Seed Initiative (GSI) program promoted production and consumption of nutrient-dense traditional African vegetables in Arusha region in Tanzania to reduce malnutrition through diet diversification. This study estimated the impact of the program on households, women of childbearing age, and children’s dietary diversity. The study used cross-sectional data from 258 program participants and 242 non-participants households and applied matching techniques to control for problems associated with unobserved heterogeneity, which could otherwise bias the outcome estimates. We compared our findings with the inverse probability of treatment weighting to correct for selection bias. We found that households participating in traditional vegetable promotion program had significantly higher dietary diversity of children under five and women in reproductive age. We found no significant impact of promotion program on households’ dietary diversity. The policy implication is that scaling up promotional activities to encourage consumers to grow and eat traditional vegetables would be an important element in initiatives to increase dietary diversity, particularly for children under five and women of childbearing age in Tanzania.