The regional mastectomy in canines is considered as an intense-pain degree surgical procedure in bitches, which requires an effective post-surgical analgesic therapy for the well-being of patients. The conventional systemic analgesic pharmacological management in oncological patients is deficient and is mainly based on non-steroidal anti-inflammatory drugs (NSAIDs) and/or low potency opioids. The present report aimed to describe post-mastectomy analgesic management in two bitches, using lidocaine as a drug-therapeutic option administered through a perilesional analgesic diffusion catheter (MILA®). Both patients were subjected to regional mastectomy. After removing the breast mass for each case, a perilesional catheter was placed and the lidocaine was administered at 2 mg/kg/hour intralesionally, by constant diffusion through a catheter and a perfusion syringe. Measurements of physiological and pain variables were collected using the University of Melbourne Scale (UMPS) in both patients every 2 hours (T0-T12) for 24 hours. Both patients showed a decrease in UMPS score during the post-surgical observation period and there were no significant changes in the measurements of the physiological variables. The intralesional infusion of lidocaine applied in the two patients subjected to mastectomy on this report achieved an effective post-surgical analgesia state.