Although an acceleration of male pubertal development has been observed, precisely which endocrine-disrupting chemicals (EDCs) might contribute to the advancing onset of puberty in boys remains unclear. Here, pyrethroids, a class of widely used insecticides that have been considered as EDCs, are proposed as new environmental risk factors. In this study, 463 boys at the age of 9-16 years old were recruited in Hangzhou, Zhejiang, China. The common metabolites of pyrethroids, 3-phenoxybenzoic acid (3-PBA), and 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), as well as gonadotropins, including luteinizing hormone (LH) and follicle-stimulating hormone (FSH), were analyzed in urine samples. Pubertal development was assessed based on Tanner stages and testicular volume (TV). A positive association between 3-PBA and gonadotropins was found (p < 0.001), in which a 10% increase in 3-PBA was associated with a 2.4% and 2.9% increase in LH and FSH, respectively. Higher urinary levels of 3-PBA in boys were associated with 275% and 280% increase in the risk of being genitalia stage 3 (G3) and G4, respectively (p < 0.05). There was a significant (132%) induction in odd of being TV 12-19 mL with increasing 3-PBA concentration compared to being in TV < 4 mL (p < 0.05). For the first time to our knowledge, this work reports on an association of increased pyrethroid exposure with elevated gonadotropins levels and earlier pubertal development in boys.