The prevalence of carcinogenic substances globally has led to an increase in malignant neoplasms. Chemotherapy, particularly using paclitaxel, is a modern, high-tech approach to treating malignancies by disrupting cell division and metabolism. Understanding the effects of paclitaxel on mammary cancer and associated pathological changes in rats is crucial for improving therapeutic outcomes. Methods: The study involved 52 white outbred female rats aged six months, divided into control (n=40) and experimental (n=12) groups. Mammary cancer was induced using 7,12-dimethylbenzanthracene, and paclitaxel was administered intravenously at a dose of 0.2 mg/kg to the experimental group. The rats' behavior, physiological state, and various histological parameters of the colon were monitored and analyzed. Results: Chemotherapy with paclitaxel in rats resulted in a 5.94% decrease in body weight compared to the control group. The colon length in the experimental group was 17.84% shorter. Morphological examination revealed significant inflammation, a decrease in goblet cells, and increased numbers of lymphocytes, macrophages, and mast cells in the colon mucosa. These changes indicate severe epithelial damage, collagen fiber thickening, and chronic inflammation, leading to mechanical damage and microbleeding in the colon tissue. Conclusion: Paclitaxel-induced chemotherapy in rats causes notable atrophic and inflammatory reactions in the colon, decreasing its functional activity. This research underscores the importance of understanding chemotherapy's side effects to mitigate gastrointestinal damage and improve cancer treatment protocols.