In this study the factors that influence rural producer organizations in facilitating smallholder farmers access to agricultural markets were studied. The study used survey data from 120 smallholder farmers (86 members and 34 non members of smallholder farmer organizations). Study sample was selected using stratified random sampling technique based on number of farmer organisations. The study employed a triangulation of data from both primary and secondary data sources. Analyses of qualitative and quantitative data were done using multinomial regression analysis and descriptive statistics. The specific objectives of the study were to analyze factors which determine smallholder farmers‟ access to agricultural markets, to assess the extent to which rural producer organizations facilitate smallholder farmers‟ access to agricultural markets and to identify problems faced by producer organizations in linking smallholder farmers‟ access to agricultural markets. The findings suggest that among the social capital indices, group trust, help, frequency of attendance in group meetings and participatory decision making influenced positively smallholder farmers‟ access to agricultural markets. Cognisant, the average per capita monthly income for group members was Tsh 13 022. However, this per capita is lower than the overall poverty line of Tsh 28 418 per person per month as defined by National Bureau of Statistics (NBS). Furthermore, the results revealed that presence of rural producer organizations is not the only solution for improved access to agricultural market. The access to agricultural market is affected by other external shocks and structural constraints ranging from low price (46%), long market chain (23%), price fluctuation (18%), lack of profitable market (8%), asymmetric market information (3%) and poor infrastructure (2%). The study concluded that farmer groups have the potential to overcome many of the marketing problems smallholder farmers face. However, there is a need for investments at the individual farmer level to participate in group dynamics. It implies that composition and characteristics of producer organizations influence the way these organizations perform their roles. Attention must therefore be given to these composition and characteristics, in the formulation and implementation of development strategies that target smallholder farmers‟ access to agricultural markets through producer organizations.