Background: Breast cancer is the most common cancer in women worldwide. Breast cancer represents about 13% of all new cancer cases in both male and female yearly and represents about 22.8% of cancer cases among female patients in Yemen. Objective: To study the early complications following modified radical mastectomy among patients diagnosed with breast cancer and evaluate some risk factors and associated comorbidity. Methods: The present prospective and observational study was conducted in Al-Gomhori teaching hospital that described complications in 50 patients with breast cancer underwent modified radical mastectomy from Jan. 2019 to Jan. 2020. Results: The mean age of cases was (45.6) years with a standard deviation of (12.4) years. Only 2 male patients (4%) were diagnosed with carcinoma breast and 48 female patients (96%) out of 50 total cases. In the 50 cases, in 23 patients (46%) chief complaint was lump in breast, followed by history of pain in lump in 18 cases (36%), then breast mass with axillary swelling in 9 cases (18%). Seroma formation was the most common complication seen in 22 (44%) patients, wound infection in 14 (28%), pain at the surgical site. Seen in 14 (28%) and flap ecchymosis in 2 (4%) cases and flap necrosis in 1 case (2%) and early lymphedema seen in 1 (2%) case. Conclusions: It was concluded that the early complications following of modified radical mastectomy included seroma formation, surgical site infection, pain and paresthesia, skin flap ecchymosis and necrosis, and hematoma.