Prostate cancer is a prevalent malignancy in men, necessitating the development of more effective treatment drugs. Alisma is commonly used in clinical settings for various ailments, including tumors. However, its mechanism of action in prostate cancer cells remains unclear. This study aimed to clarify the effects of Alisma orientale extract (AOE) on prostate cancer. Our results showed that AOE inhibited prostate cancer cell growth and induced apoptosis while promoting oxidative stress. Mechanistically, AOE modulated the p38/nuclear factor kappa-B (NF-κB) pathway to inhibit prostate cancer progression. Taken together, these findings suggest that AOE could serve as a potential treatment for prostate cancer.