The study investigated the effect of non-use of external on food security of small holder farmers: A case of Kiruhura District, Uganda. The key objective that guided the study was to assess the effect of moderate use of external inputs on food security of small holder farmers in Kiruhura District. A cross-sectional design using mixed methods approach was used to answer the study questions. The sample size for the study was 327 with 310 respondents participating in the study hence giving the average response rate of 91.4%. Stratified random sampling and purposive techniques were used to select the participants. Data analysis involved frequencies, means and inferential statistics such as correlations and the coefficient of determination. Findings revealed that smallholder farmers heavily rely on rainfall for water and employ rudimentary tools, animal manure, and plant leaves for farming. Weather uncertainties limit year-round cultivation, impacting agricultural quality and contributing to food insecurity. The study suggests that non-use of external inputs hampers food security, recommending a government-led campaign, through the Ministry of Agriculture, Animal Industry, and Fisheries in Uganda, to raise awareness about modern farming methods.