Abstract: Cisplatin and other platinum complexes are important chemotherapeutic agents and useful in the treatment for several cancers such as prostate, ovarian and testis. However, severe side effects including reproductive toxicity of cisplatin and other platinum complex cause limitations in their clinical usage. In this context, we aimed to compare the damage in testis caused by cisplatin and a novel platinum-N-heterocyclic carbene complex (Pt–NHC). To this end, 35 Sprague–Dawley rats were divided randomly into five equal groups (n = 7 in each group). Cisplatin and Pt–NHC were intraperitoneally administered as a single dose of 5 mg/kg or 10 mg/kg, and the rats were then killed 10 days after this treatment. The testicular tissues and serum samples were taken from all rats for the determination of reproductive toxicity. The results showed that cisplatin and Pt–NHC caused toxicity on the reproductive system via increased oxidative and histological damage, decreased serum testosterone levels and negatively altered sperm characteristics in a dose-dependent manner (p < 0.05). At the same dose levels, cisplatin generally caused lower toxicity on the reproductive system compared with Pt–NHC. In conclusion, these results suggest that Pt–NHC has more toxic effects on the male reproductive system than cisplatin, and in terms of clinical usage, Pt–NHC may be unsafe compared with cisplatin.