Aim of this study was to evaluate sexual desire, physical semen characteristics, and some blood biochemical parameters of buffalo bulls injected with tonophosphane during summer season. Total of 20 sexually mature Egyptian buffalo bulls with average of 4 years of age and 600 kg live body weight were divided into 4 experimental groups (5 bulls in each). Bulls in the 1^st group (G1) were served as a control and did not receive any treatment. However, each bull of those in the 2^nd (G2), 3^rd (G3) and 4^th (G4) groups was once weekly administrated by intramuscular injection with 5, 7 and 10 ml of tonophosphane for 8 weeks (treatment period). Reaction time (RT) and scrotal circumference (SC) were recorded, semen was collected by artificial vagina and evaluated, and blood samples were taken for 12 weeks. Results showed that RT decreased (P<0.05), SC increased (P<0.05) by increasing treatment level, being the lowest in G2 and the highest in G4. All physical semen characteristic (ejaculate volume, mass and progressive motility, sperm livability, sperm cell concentration and sperm abnormality) were the best (P<0.05) in G4. Sperm outputs per ejaculate as total motile, live and normal sperm output per ejaculate increased (P<0.05) in G4. Plasma total proteins and albumin concentration increased (P<0.05) in treatment groups, while globulin concentration increased only in G3. By advancing collection week, RT, SC, ejaculate volume, abnormal sperm, sperm cell concentration, all sperm outputs (P<0.05), and mass and progressive motility (P≤0.05) improved, while live sperm decreased (P≤0.05). In conclusion, intramuscular injection with tonophosphane as a phosphorus source once weekly pre-collection of semen showed pronouncedly positive effects on sexual desire, semen quality and health status of Egyptian buffalo bulls. Tonophosphane injection at a level of 10 ml/head showed the best results.