Food insecurity remains a persistent challenge in many low- and middle-income countries, yet the role of household structure in shaping vulnerability remains insufficiently understood. This study examines how transitions in household headship affect food insecurity in Nigeria using panel data from the Nigeria General Household Survey Panel (GHS-Panel), focusing on households observed in both Wave 4 and Wave 5.The analysis exploits within-household variation in headship status using household fixed effects models, which control for time-invariant household characteristics and common time shocks. This approach allows for identification of how changes in household leadership, particularly transitions into female-headed households, are associated with changes in food insecurity over time. Additional analyses explore heterogeneity across geographic contexts, including rural versus urban locations and regional differences, and examine the role of credit participation and exposure to shocks. The results indicate that households transitioning into female headship experience higher levels of food insecurity relative to households that remain male-headed. In contrast, transitions into male headship are associated with reductions in food insecurity. The findings further show that the effects of female headship are stronger in rural areas and vary across regions, with more pronounced impacts observed in northern Nigeria. While credit participation does not have a strong direct effect on food insecurity, there is suggestive evidence that it may partially mitigate the negative effects associated with transitions into female headship. Overall, the findings highlight the importance of household structure, gender dynamics, and economic vulnerability in shaping food security outcomes. The results suggest that policies aimed at reducing food insecurity should consider targeted support for households undergoing structural transitions, particularly those becoming female-headed, as well as broader efforts to improve access to resources, social protection, and financial inclusion.