This paper conducts ex-ante impact assessments for policy interventions to promote amaranth value chains in Tanzania and Kenya. Amaranth is an underdeveloped, drought-resistant, and nutrition-rich crop used for human food, animal fodder, and ornamental purposes. Promoting amaranth value chains is a difficult task, given that amaranth is not a well-established commodity and has limited market outlets in the developing world at present. This paper provides a framework within which conduct scenario analysis of ways to promote amaranth value chains using system dynamics (SD). We constructed an integrated amaranth production and market model to evaluate the impact of producer adoption of improved production technologies (improved seed varieties), and changes in demand for amaranth products, on producer profits and planting behaviour. The results of our model show that the profitably upgrading and commercialising of amaranth value chains require multifaceted and chain-level interventions that improve supply- and demand-side conditions. Interventions that target only the supply side serve to increase amaranth production, but generate minor economic gain for producers.