Background: Breast cancer is one of the most common cancer throughout the world & a leading cause of cancer related female mortality within the 2nd–6th decade of life. Mastectomy is the mainstay option for most cases of carcinoma breast till date. Post mastectomy seroma formation remains not only a common complication but also a agonising event for both the patient and operating surgeon. Materials & Methods: A prospective study was carried out on 50 female patients who presented to the surgical OPD of IMS & SUM Hospital between July 2015 to July 2017. After obtaining an exhaustive history a thorough clinical examination done, followed by required investigations and posted for surgery. All post–operative findings were recorded under specific parameters. Results & Conclusions: Seroma remains the most common post–op complication following mastectomy for carcinoma breast. Use of electro cautery is significantly associated with causation of seroma, hence against injudicious use of cautery during breast surgeries. Persistent drain output beyond a week should alert the possibility of seroma formation. Treatment of seroma should initially be limited to observation if seroma is small, followed by repeated aspiration if collection is significant, however if recurrence occurs even after 4 aspirations re–insertion of drain should be planned.