A novel fungal phytase (NFP) was evaluated for its effects on growth performance, phosphorus (P) metabolism, tibia development, and nutrient digestibility in broilers. A total of 420 one-day-old Arbor Acres broilers were randomly assigned to seven treatments: a negative control (basal diet without phytase), a positive control (500 U/kg commercial phytase), and five groups supplemented with NFP at 250, 500, 1000, 1500, or 2000 U/kg. Increasing inclusion of dietary NFP linearly improved average daily gain and feed conversion ratio (FCR) during days 22–42 and overall, with NFP outperforming commercial phytase at equivalent doses in FCR reduction. NFP increased the digestibility of crude fiber and P, linearly increased crude protein digestibility, and dose-dependently enhanced ileal digestibility of several amino acids (especially at 1000–2000 U/kg). NFP dose-dependently increased plasma inorganic P while reducing alkaline phosphatase and parathyroid hormone. Tibia weight, midshaft width, bone density, breaking strength, and P content increased linearly with NFP, peaking at 1000–2000 U/kg. NFP also upregulated tibial mRNA expression of the phosphate-regulating gene with homology to endopeptidase on the X chromosome, dentin matrix protein 1, and osteocalcin. In conclusion, NFP optimizes broiler growth, nutrient utilization, and skeletal development via dose-dependent modulation of P metabolism and osteogenic pathways.