The sexual maturation in all mammals is the period in which the quiescent gonads are activated by gonadotropins from anterior pituitary, increasing the secretion of sexual hormones. Sexual maturation it is also related with the development of several other body features such as body mass and maturation of the circulatory, skeletal and hematopoietic systems. The aim of the present study was to evaluate the function of neutrophils submitted to in vivo lower and higher concentration of testosterone (sexually immature: 60 days and sexually mature: 90 days). Using different approaches we evaluated cell viability and function and gene expression in rat neutrophils from 60 and 90 days-old animals. Neutrophils from 90 days-old rats showed a decrease in phagocytic and fungicidal capacity, without change in cellular viability. Additionally, we verified that sexual maturation induced increase in production of reactive oxygen and nitrogen species (RONS) and also in TNF-α, IL-6 and IL-10 cytokines. In conclusion, our data suggest that increase in testosterone levels induced significant alteration in neutrophil function, impairing phagocytic capacity.