Because of high water loss and rot observed in postharvest sweet potato ( Ipomoea batatas (L.) Lam.) roots, a carnauba wax (CW)-based nanoemulsion without or with glycerol monolaurate (CW-GML) was developed by a high-energy emulsification approach. The effects of the two coatings on decay, respiration rate, weight loss, surface color, total soluble sugar, and starch content as well as the sensory quality of sweet potato roots were investigated during storage at 20°C for 50 days. Compared with the control treatment (water) and CW coating alone, CW-GML coating exhibited higher emulsion stability and antifungal activity, and treatment resulted in a uniform and continuous coating on roots. The CW-GML and CW coatings both effectively reduced root weight loss and respiration rate and inhibited decay incidence compared with control roots during storage. The CW-GML coating showed markedly stronger inhibition of root rot than the CW coating. Both the CW-GML and CW coatings promoted an increase in root sweetness but did not negatively impact perceived flavor. The overall results demonstrate that the CW-GML coating holds great promise as an effective postharvest technology to preserve food quality and extend shelf life of sweet potato roots.