South Sudan faces serious problems of food insecurity due to low levels of domestic food production, periodic droughts, widespread poverty, and since late 2013, renewed armed conflict. This article explores market price behavior using cointegration analysis and estimates the effects of production and trade shocks through multimarket model simulations. We show that market prices in the capital city, Juba, of both maize and sorghum are cointegrated with import parity prices of these cereals sourced from Uganda, consistent with observed trade flows. Model simulations, using econometrically estimated demand parameters, suggest that private sector imports of maize and wheat would greatly mitigate the potential fall in consumption in the case of a decline in domestic cereal production. Other simulations indicate that if total imports of cereals are reduced by one‐third (still more than two times the levels of food aid in 2013) because of disruptions to private market flows, domestic prices of cereals could rise by 45% or more. The article concludes that whatever measures are taken involving national food security reserves, it is crucial that government policy serves to maintain incentives for private sector imports to avoid destabilizing market supplies, domestic prices, and ultimately, food consumption of the poor.