This study assessed the impact of climate variability on household food security in Borno State, Nigeria, a semi-arid region simultaneously affected by protracted conflict and environmental stress. The research was motivated by increasing evidence of rising temperatures, erratic rainfall patterns, recurrent flooding, and their compounded effects on agricultural productivity and household welfare. Adopting a descriptive survey design, the study sampled 400 households across selected local government areas using a multistage sampling technique. Primary data were collected through a structured and validated questionnaire (Cronbach’s alpha = 0.82), while secondary climate data spanning three decades (1990–2026) were analyzed to determine trends in temperature and precipitation. Descriptive statistics, correlation analysis, and multiple regression techniques were employed to examine the relationships between climate variability indicators and household food security outcomes. Findings revealed that household food security in Borno State is critically compromised across the four dimensions of availability, access, utilization, and stability. Approximately 6 million people lack basic food supplies, while 15,000 individuals face catastrophic hunger (IPC Phase 5 conditions). Vulnerable populations, particularly internally displaced persons (IDPs), women, and children, experience disproportionately higher levels of food insecurity compared to non-displaced farming households. Climate trend analysis showed a significant rise in temperature ranging between 1.5°C and 2.6°C over the past three decades, alongside a 15% decline in long-term annual rainfall and increasing precipitation volatility. Statistical results indicated strong negative correlations between climatic variables and staple crop yields: rising temperature was associated with a 27% reduction in rice yields (r = -0.82, p < .01), while reduced rainfall significantly affected groundnut (22% decline, r = -0.76, p < .05) and guinea corn production (18% decline, r = -0.70, p < .05). The study concludes that climate variability significantly and adversely affects household food security in Borno State, with conflict dynamics amplifying vulnerability and limiting adaptive capacity. Strengthening early warning systems, scaling climate-resilient agricultural infrastructure, enhancing institutional support, and implementing integrated, conflict-sensitive adaptation policies are essential for building sustainable and resilient food systems in the region.