Abstract Food price volatility has posed a persistent challenge in Ethiopia for more than five decades, raising concerns about its long-term implications for child survival in the context of chronic food insecurity. Although previous studies have explored food prices and child health, little is known about how the dynamics of food price volatility influence under-five mortality across different time horizons. This study aimed to quantify the dynamic and asymmetric effects of food price volatility on under-five mortality in Ethiopia from 1970 to 2020. The analysis uses annual national data and applies Fourier-based Autoregressive Distributed Lag and nonlinear Autoregressive Distributed Lag models, which allow for structural breaks, nonlinear adjustments, and differing responses to increases and decreases in volatility. The results show a stable, long-run relationship among the variables. Food price volatility raises under-five mortality mainly over medium and long horizons, while short-run effects are weak and statistically insignificant. Economic growth, government effectiveness, and access to basic sanitation are associated with sustained reductions in under-five child mortality rates. The nonlinear estimates reveal strong asymmetry, with declines in food price volatility producing larger improvements in child survival than the mortality increases associated with comparable rises in volatility. Frequency-domain Granger causality tests further indicate that food price volatility primarily predicts under-five mortality at medium- and long-term frequencies. These findings highlight the need for policies that stabilize food prices, strengthen institutional capacity, reduce reliance on out-of-pocket health spending, and expand access to basic health and sanitation services to mitigate the long-run mortality risks associated with economic instability in Ethiopia and similar low-income settings.