Rain Water Use Efficiency (RWUE) of sweet potato under cattle-cud mulches was investigated with the aim of identifying appropriate cattle-cud mulch rates for managing the fragile soils of the humid tropics to ensure sustained productivity of sweet potato. Experimental units measuring 9m2 each were used and sweet potato vines were planted at the spacing of 1 x 0.5m2. Cattle-cud mulches at rates of M0, M10, M20 and M30 tons ha-1 were administered to the different plots. Yield parameters of sweet potatoes as well as rainfall data for the period were collected. Data were assessed using the Analysis of Variance and correlation analyses were also performed to determine the relationships between soil and crop parameters. Results showed that RWUE of 2.38 from M30 plot was significantly higher than other treatments. This correlated with significantly (P<0.05) high tuber girth (19.0cm), tuber length (21.0cm), marketable size (32.33 cm) and number of tuber yield (60.50). Also, organic matter content of the soil receiving M10 (3.60%) and M20 (3.04%) cattle-cud mulches were significantly higher than M0 (2.96%). The use of cattle-cud as a mulch material significantly increased RWUE and also improved the yield and yield component of sweet potato.