The available phosphorus (P) in acid sulfate soils (ASSs) is low because of fixation by aluminum (Al) and iron (Fe), resulting in decreased P use efficiency and crop yield. At present, the use of dicarboxylic acid polymer (DCAP) coated on P fertilizer is expected to improve P use efficiency and plant productivity. However, the influence of DCAP on P solubility and on the yield of sweet potato cultivated in acidic soils has not been elucidated. Thus, the aimed of this study was to evaluate the effect of the use of DCAP-coated P fertilizer on the availability and nutrient uptake of P as well as the yield of sweet potato. Under the greenhouse condition, the use of DCAP significantly improved P availability (~3 mg P kg-1), increasing tuber diameter and length by ~0.5 and ~1.0 cm, respectively. Thus, the productivity of sweet potato in the treatment 40- kg P2O5 and 60-kg P2O5 ha-1 coated with DCAP was higher by about 100 g pot-1 than that in the same rate of P fertilizers (40- and 60-kg P2O5 ha-1) not coated with DCAP. In the field experiment, P accumulation (82.7 kg P2O5 ha-1) and tuber yield (22.0 t ha-1) in the treatment of DCAP-coated with 60-kg P2O5 ha-1 were not significantly different compared with that in the treatment of 80-kg P2O5 ha-1 (82.1 kg P2O5 and 21.7 t ha-1, respectively). Furthermore, the use of DCAP combined with 75% P fertilizer increased the P availability by the same amount as that with the use of 100% P fertilizer. Hence, the use of DCAP reduced about 25% of the chemical P fertilizer applied in soil.