This study evaluated the impact of Promoting Sustainable Agriculture Project in southern Borno State, Nigeria (PROSAB) on food security, farm income and rural livelihoods of households. The major objective of the study was to evaluate the impact of PROSAB on food security, farm income and rural livelihoods. The specific objectives were to describe the socio-economic characteristics of households, their livelihoods and asset ownership, determine and compare the farm incomes and farm profitability of PROSAB and non-PROSAB households, compare food security status of households in the project area and non project area and compare food security status in the project area with that in 2004 and, identify constraints faced by farmers in the project area and assess the perception of women, men, and youth groups (farmers) on the impact of the project. Using a multistage sampling technique, three out of the four LGAs under the project were covered. The three LGAs were selected at random to include Biu, Hawul and Kwaya Kusar LGAs. Two communities from the list of the 39 communities in the project area were selected. In each of the selected communities, a random selection of 20 households was carried out giving a total of 180 households. Using similar procedures, 180 households were randomly selected from the non project area LGAs of Shani and Bayo to serve as counterfactuals. Secondary data was generated from publications and records of the PROSAB project. The study employed analytical tools such as descriptive statistics, budgetary analysis, food security index, logit regression analysis, double difference estimator and consumer price index (CPI). The socio-economic characteristic of household heads shows that the primary occupation among PROSAB households (84.4%) as well as non-PROSAB households (58.9%) was farming. Similarly, farming was found to be the major secondary occupation among PROSAB households (15%) as well as among non-PROSAB households (30%). Bicycles were ranked first among the household assets among PROSAB households (16.4%) as well among non-PROSAB households (14.3%). The gross margin for crop based enterprises was higher among PROSAB households (N111,295.63) per ha compared to N88,006.96 per ha among non-PROSAB households and was found to be statistically significant at 5% level of probability. The food security status of PROSAB households was higher (57.2%) compared to non-PROSAB households (35.6%). The food security status in the project area increased from 42% in 2004 to 57.2% in 2010. Gender, age, use of modern farm inputs and membership of a cooperative society were found to be statistically significant at 1% level of probability while number of extension visits was statiscallys significant at 5% level of probability. Own production was the major source of food for PROSAB households (71.1%) and non-PROSAB households (61.3%). The major source of animal protein was purchase from the market for both PROSAB households (71%) and non-PROSAB households (71.1%). Inadequate storage facility was the major cause of food shortage among PROSAB households (23.3%) as well as among non-PROSAB households (26.1%). The Double Difference Estimator (DDE) was positive for maize (N373,221), soybean (N379,484), cowpea (N204,458), sheep (N773,208), and goats (N401,709), cars/pick-ups (N57) and new houses/renovated houses (N62) signifying impact. The three major constraints faced by farmers in 2004 were low yield and production, inadequate market for farm produce/low prices and inadequate farm credit. However, in 2010, the three major constraints faced by the farmers were low extension visits, inadequate fertilizer and inadequate agrochemicals. This study concluded that PROSAB impacted positively on the beneficiaries as there was an increase in the number of households that were food secure. It was recommended that more attention should be placed on the education of households, in the project area as well as in the non project area and that farmers in the project and non project areas should establish functional community based organizations as a way of assisting them to have access to credit.