University College Dublin (Ireland)About three out of every four income-earners in Tanzania are small-scale farmers and food insecurity remains a chronic problem for many of them. Around 48% of households in rural areas were either moderately or severely food energy deficient in 2011 and 39% of rural children under 5 years were stunted in 2013. To improve food security in Tanzania, it is important to understand the existing farming systems and their relationship with household food security. This study was conducted in two distinctly different agro-ecological zones of Tanzania, namely Kishapu and Mvomero Districts, to determine the main factors which influence farm households’ choice of farming systems and how these associate with food security. Data were collected during both pre- and post-harvest seasons in 2014 from 506 farm households, and augmented with market surveys, key informant interviews and focus group discussions. Four main farming systems were identified based on: crops cultivated; degree of market orientation for particular crops; and the number of livestock units owned. Household food security status was measured and a combination of Expected Utility Theory and Theory of Planned Behaviour used to analyse the factors associated with household choice of farming system. The study found that households which diversified their income sources through off-farm activities were more likely to have better food access in the lean (pre-harvest) periods. The factors influencing decisions on farming systems were related to the household size, farming context and farm characteristics. In the semi-arid and remote areas of Kishapu, larger households were more likely to choose a Mixed Crop and Livestock farming system, indicating that larger family size ensured the supply of needed labour for both livestock keeping and cropping activities. In the higher rainfall and more accessible district of Mvomero, households were more likely to practice a Single Food Crop farming system and were compelled to seek out off-farm work. The study recommends that strategies to improve food security in rural areas should attempt to: enhance income from farming, promote off-farm income generating activities, and promote behavioural change communication on what is culturally regarded as food in the study area.