In order to analyze the effect of NAFTA on the North American sweet potato market, this study uses both observable trade data such as trade volumes and home prices and unobservable trade data such as imported prices and non-tariff trade costs. The unobservable trade data are estimated by the model used in this study. Unlike previous studies, this study confirms that the degree of integration in the North American sweet potato markets is relatively low because the three individual sweet potato markets are mostly dominated by their own product and the difference between home and imported prices in each NAFTA member country have increased from pre-NAFTA to post-NAFTA levels. Two counterfactual analyses confirm that low levels of market integration may be due to high non-tariff trade costs.