The prostate gland, an androgen-dependent organ, plays a pivotal role in male fertility. Bilateral castration, employed for therapeutic and preventive purposes in both humans and animals, prompted our investigation into the histological architecture of the prostate gland post-orchiectomy in adult male dogs. Six apparently healthy male mongrel dogs (18–20 kg, 12–24 months) were divided into Control and bilateral castrated groups. A blood testosterone test was conducted, and prostatic tissues were harvested on day 20 for basic histological, histochemical, and immunohistochemical studies. Results revealed a rapid decline in serum testosterone levels, concomitant with significant histological alterations in the prostate gland. Notably, there was a substantial reduction in epithelial height and a noticeable decrease in the immunostaining affinity of androgen receptors. Additionally, a marked interstitial thickening, characterized by a significant increase in the percentage of collagen fibers, was observed. In conclusion, bilateral castration induces changes in prostatic histological architecture alongside a depletion of blood testosterone levels. These findings contribute to our understanding of the impact of castration on male reproductive organs, potentially informing therapeutic and preventive strategies for androgen-dependent conditions.