Phosphorus is considered an essential element for sugarcane, assuming great importance in rooting, tillering and final stem yield. In order to evaluate the effects of pre-planting phosphating on the internal morphology of sugarcane leaves, an experiment with the RB867515 variety was carried out in a randomized block design with 4 replications, in a factorial scheme 2x4, being two sources of phosphorus (decanted phosphate and monoammonium phosphate) and four doses of phosphorus (0; 80; 120; 160 kg ha-1 P2O5). At 120, 240 and 362 days after planting the following characteristics were evaluated: Abaxial epidermis thickness, adaxial epidermis thickness, mesophyll thickness, phloem vessel diameter and phloem vessel diameter. Phosphorus doses influenced the development of sugarcane leaf-bearing vessels at harvest. Concentrations above 160 kg ha-1 the P2O5 presented lower mean phloem diameter values in sugarcane leaves. Concentrations with 80 kg ha-1 the P2O5 presented greater xylem diameter in sugarcane leaves.