Canine mammary gland tumors (CMGT) are among the most prevalent neoplasms in female dogs, with a higher incidence observed in those not spayed at an early age. Given this context, clinical cases of dogs with mammary tumors presenting at the Small Animal Clinics of Madras Veterinary College, Chennai, were studied to evaluate the anticancer effect of paclitaxel on CMGT in clinical cases. A total of forty-three CMGT-positive dogs were identified and underwent tumor excision following a standard surgical protocol. Tumor type and grade were confirmed based on established selection criteria. Of these, ten dogs were included in the study and received paclitaxel chemotherapy. Pre- and post-surgical levels of cancer-associated serum biomarkers, including CA15.3, CEA, COX-2, and HER-2, were assessed. Elevated levels of these biomarkers were noted in pre-surgical samples, while marked reductions were observed on days 21, 42, and 63 post-chemotherapy, suggesting a lack of metastasis and non-recurrence of mammary cancer. Clinical examinations confirmed the absence of cancer recurrence in the treated dogs up to day 120. In post-surgical cases of CMGT, paclitaxel was effective in preventing recurrence and metastasis of mammary cancer. However, further research using induced cancer models in animals, as well as clinical studies involving larger sample sizes and extended observation periods, is necessary to confirm paclitaxel's efficacy in CMGT-positive female dogs.