Background/Aims: JTT-751 (ferric citrate hydrate) is a novel iron-based phosphate approved in Japan for the treatment of hyperphosphatemia in dialysis and nondialysis patients with chronic kidney disease. Methods: In this phase 3, multicenter, open-label, dose-adjusted study, we investigated the efficacy and safety of JTT-751 in peritoneal dialysis patients. A total of 56 patients with serum phosphate ≥5.6 and <10.0 mg/dl were enrolled in the study. The dose of JTT-751 was adjusted to between 1.5 and 6.0 g/day, according to the target range of serum phosphate (3.5-5.5 mg/dl), for 12 weeks. The primary endpoint was change in serum phosphate from baseline to end of treatment. Secondary endpoints included the percentage of patients achieving target serum phosphate levels and changes in intact parathyroid hormone. Results: Serum phosphate was significantly reduced by 2.26 mg/dl (p < 0.001). The percentage of patients achieving target serum phosphate levels was 76.8%. Intact parathyroid hormone decreased significantly (p < 0.001). The most common adverse drug reactions were diarrhea and constipation. Most of the events were considered to be mild. Treatment with JTT-751 resulted in significant increases in serum ferritin and transferrin saturation (p < 0.001). Conclusion: In peritoneal dialysis patients with hyperphosphatemia, 12-week treatment with JTT-751 resulted in significant reductions in serum phosphate while simultaneously increasing serum iron parameters. JTT-751 was well tolerated.