This study aimed to determine the antioxidant capacity of the Leucaena leucocephala aqueous shoot tips plus young leaves (LL-spl) extracts among three different fractions (LL-spl 10, 20, and 40 min) and to examine its acute toxicity on male reproductive parameters. The amount of the total phenolics in LL-spl extract was determined using a Folin-Ciocalteu reagent method and its antioxidant capacity was analyzed using 1,1-diphenyl 1-2-picrylhydrazyl radical scavenging and ferric reducing antioxidant powder methods. The LL-spl extract fraction with highest antioxidant capacity was used in animal treating. Male rats were divided into three groups (n=5); control and groups treated with LL-spl 400 and 600 mg/Kg body weight for consecutive 40 days. The results showed that the LL-spl 40 min fraction possessed the highest antioxidant capacity. In addition, the LL-spl 400 and 600 groups showed no differences in weights of body, testis and epididymis, serum testosterone levels, and expression of testicular steroidogenic acute regulatory (StAR) protein. Significantly, LL-spl extract reduced the weight of seminal vesicle, sperm concentration, and seminiferous diameters compared with control. Moreover, LL-spl extract had adverse effect on testicular histology in inducing of seminiferous atrophy and degeneration including dilated blood vessels in interstitial tissue. It was concluded that although LL-spl extract possessing antioxidant capacity, in short term consumptions, it could be toxic to some male reproductive organs especially damaging testicular tissues.