This study aimed to evaluate dietary supplementation of Moringa oleifera leaves (MOL) on semen quality, oxidative stress, thermal regulation and health status of heat stressed buffalo bulls. Eighteen sexually mature Egyptian buffalo bulls were divided into three groups, 6 in each. Bulls in G1 were fed ration composed of concentrate fed mixture (CFM), berseem hay and rice straw (control). Bulls in G2 and G3 were fed the same CFM supplemented with MOL at levels of 4 and 8% of CFM, respectively for one month pre-semen collection and 4 months as semen collection period. Semen was collected twice weekly and evaluated for percentages of individual motility (IM), livability (SL), abnormality (SA) and damaged acrosome (DA) of sperm cells. Response of spermatozoa to hypo-osmotic test (percentage of curled spermatozoa) at 50 mOsm/l for 30 min was also recorded. Rectal (RT) and skin (ST) temperatures, respiration rate (RR) and pulse rate (PR) were recorded. Blood samples were taken pre-treatment and during 1^st, 2^nd, 3^rd and 4^th months of semen collection to determine hemoglobin concentration (Hb), packed cell volume (PCV%), count of red (RBCs) and white (WBCs) blood cells. Concentration of total proteins (TP), albumin (AL), globulin (GL), glucose (GLU), triglycerides (TG), total cholesterol (TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL), urea, uric acid, creatinine (Cr) and testosterone, as well activity of AST, ALT, superoxide dismutase (SOD), catalase and glutathione (GSH) were determined in blood serum. Concentration of TG and TC, and activity of AST, ALT, SOD, catalase and GSH were estimated also in seminal plasma. Results showed that RT and ST, RR and PR decreased (P<0.05) in G3 than in G2 and G1. Each of RT and ST, RR and PR increased (P<0.05) up to 3^rd collection month, then decreased at the 4^th collection month in association with THI values. Percentage of IM, SL, SA, CT and DA were improved (P<0.05) in G2 and G3 as compared to G1, being the best (P<0.05) in G3. All previous parameters were improved (P<0.05) by advancing collection month. Both TC and TG in seminal plasma decreased (P<0.05) in G3 as compared to G1 and G2. Activity of AST and ALT decreased (P<0.05), while catalase, GSH and SOD activities increased (P<0.05) in seminal plasma of G2 and G3 as compared to G1. Each of TC, ALT, catalase, GSH and SOD in seminal plasma increased (P<0.05), while TG decreased (P<0.05) by advancing collection month, while AST was not affected. Serum testosterone con­centration was higher (P<0.05) in G2 and G3 than in G1, being the highest in G3. Each of PCV, Hb and RBCs were higher (P<0.05) in G2 and G3 than in G1, being the highest in G3, while WBCs showed (P<0.05) an opposite trend (P<0.05). Each of Hb, RBCs and WBCs increased (P<0.05) one month after treatment, then Hb and RBC increased (P<0.05), while PCV and WBCs decreased (P<0.05) at the 4^th collection month. Serum TP, AL and GLU increased (P<0.05) in G3 as compared to G1 and G2, while GL was not affected by treatment. By advancing collection month, concentration of TP, AL, GL and glucose showed gradual increase (P<0.05). Concentration of TG and TC reduced (P<0.05) in G2 and G3, while HDL increased (P<0.05) in G3 as compared to G1. However, LDL was not affected by treatment. Concentration of TG decreased (P<0.05), while HDL increased (P<0.05) by advancing collection month. Concentration of TC and LDL showed fluctuated trend of change at different collection months (P<0.05). Serum urea decreased (P<0.05) in G3, while uric acid, creatinine, AST and ALT decreased (P<0.05) in G2 and G3 as compared to G1. Urea and uric acid decreased (P<0.05) during one month before semen collection and at the 3^rd collection month, respectively. However, Cr, AST and ALT decreased (P<0.05) by advancing collection month. Catalase, GSH and SOD increased (P<0.05) in G2 and G3, being the highest in G3. All antioxidant enzymes increased (P<0.05) by advancing collection month, being at higher rate for SOD, followed by GSH and the lowest for catalase during month pre-treatment. The current study can conclude that, moringa oleifera leaves could be used as feed additive to help farmers for sustainable development of breeding bulls. Results of this study recommended that daily adding 240 g moringa oleifera leaves per buffalo bull for one month pre-semen collection or at a level of 8% of concentrate feed mixture in diets of buffalo bulls can improve quality and production of semen without any adverse effects on health status under hot climatic conditions in Egypt.