Paranonylphenol (p‐NP) is an environmental pollutant that causes oxidative stress. The purpose of this study was to evaluate the protective effect of N‐acetylcysteine (NAC) as an antioxidant on sperm parameters and testis in mice after treatment with p‐NP. Adult mice were randomly divided into four groups (n = 6, each group) includ‐ ing 1‐control, 2‐ p‐NP (250 mg kg −1 day −1 ), 3‐ NAC (150 mg kg −1 day ) and 4‐ p‐ NP + NAC. After 35 days of oral treatment, the mean of spermatogenic index (p < 0.02), sperm count (p < 0.01), daily sperm production (p < 0.01), sperm tail length (p < 0.02), progressive movement (p < 0.04), normal morphology (p < 0.04) and via‐ bility (p < 0.01) of spermatozoa and also serum testosterone level (p < 0.04) were significantly reduced in p‐NP group when compared to other groups. While the count of the positive TUNEL cells in the seminiferous tubules (p < 0.01) and level of the malondialdehyde (MDA) in testis (p < 0.02) and serum (p < 0.01) significantly in‐ creased. In the histopathologic assay in the p‐NP group, apoptosis, atrophy, oedema, reduction in sperm density in lumens and vacuoles were observed. The findings of this study indicate that NAC as a potent antioxidant be able to compensate the ad‐ verse effects of p‐NP in spermatogenesis, testis and levels of testosterone and MDA in the p‐NP + NAC group significantly compared to the p‐NP group.
