Ensuring food security remains a significant challenge for rural farming households in Nigeria, where fluctuations in agricultural productivity directly affect household welfare and nutritional outcomes. Accordingly, this study investigates the relationship between cassava yield and household food security among cassava-farming households in Nigeria, using nationally representative data from the 2018–2019 Nigeria General Household Survey (GHS-Panel). Despite Nigeria’s global leadership in cassava production, widespread food insecurity persists among cassava producers, revealing a paradox between national output and household food security outcomes. To address this paradox, the study employed descriptive statistics, Box–Cox regression, and truncated Poisson regression models to identify the key factors influencing cassava yield and food security. The Box–Cox regression results show that age, access to credit, farm size, and the use of improved cassava varieties significantly affect cassava yield. Furthermore, the truncated Poisson model indicates that cassava yield, income, and access to water positively and significantly enhance household food security, whereas age, household size, and food expenditure exert negative effects. These findings highlight that improvements in yield alone are insufficient to guarantee food security unless they are complemented by access to credit, reliable water resources, and income diversification opportunities. The study therefore concludes that policies promoting the adoption of improved cassava varieties, youth participation in agriculture, expanded rural credit access, and irrigation development are crucial for enhancing productivity and achieving sustainable food and nutrition security among cassava-farming households in Nigeria.