The aim of this study is to investigate the potential antioxidant and anti-inflammatory effects of thymoquinone (TQ) to improve acute bacterial prostatitis (ABP) induced by Pseudomonas aeruginosa. A total of 42 male Wistar albino rats were divided into 7 groups as follows: control, ABP (24, 48, and 72 h), and TQ-ABP (24, 48, and 72 h). The prostate tissue samples were assayed for prostate tissue malondialdehyde (MDA) and nitric oxide (NO) levels, and catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPX) activities. Sections were examined for characteristic histological changes, and a histological scoring system was used. When the ABP groups given TQ (24, 48, and 72 h) were compared to the ABP groups not given TQ, the levels of MDA and NO and the GPX activity were found to be significantly lower in the groups given TQ. Concerning SOD values, the TQ-ABP-72 group was lower in comparison with the ABP-72 and control groups, but statistically higher than the TQ-ABP-48 group (p < 0.05). Concerning CAT activity, only the TQ-ABP-72 and ABP-72 groups had a significant difference with the control group. TQ improved prostate histology significantly only in the TQ-ABP-24 group compared to the ABP-24 group (p < 0.001). Our study demonstrated for the first time that ABP induced by P. aeruginosa had an oxidative effect on prostate tissue and could regress following TQ administration as shown with the biochemical and histological findings.