This study was conducted to analyze cassava and sweet potato value chains so as to identify potential areas for intervention in order to improve small-scale farmers’ access to markets in Mvomero and Kongwa Districts. Sub-sector mapping was used to map cassava and sweet potato value chains. Results indicate that several constraints exist in the two sub-sectors which among other things include low production, poor access to inputs, lack of market information, poor support services, poor linkages, lack of value addition and poor infrastructure. Profit and marketing margins along the cassava and sweet potato value chains were computed. Results indicate variations in gross margins with the highest gross margin of 34 355 Tshs/90kg obtained by local processors while the farmers’ gross margin was 24 709.31 Tshs/90kg. For the case of sweet potatoes, the highest gross margin of 29 884.41 Tshs/90kg was obtained by farmers while local processors’ obtained the lowest gross margin of 3050 Tshs/90kg. Regression analysis model was used to analyse the determinants of cassava and sweet potato farmers’ profitability. The findings show that farm size, experience of household head and farm location were the main determinants of farmers’ profitability. Convention method, Shepherd’s method and Acharya’s modified marketing efficiency methods were applied to determine the marketing efficiency at different channels of cassava and sweet potato marketing system. Results indicate that market efficiency in all the two sub-sectors decreases as the marketing costs and/or margins of intermediaries in the marketing channels increases and vice versa. In conclusion, the two sub-sectors in general face a number of challenges that hinder the development of a sustainable and profitable value chain. Therefore, it is recommended that the challenges need to be addressed by involving government, researchers and private parties in establishing a sustainable and profitable cassava and sweet potato value chains.IDRC, through the CGP project