All surgeries, from minor procedures, such as sutures, to major surgeries, such as open abdominal surgery, carry with them risk for complications. Among the most frequently encountered complications are surgical site infections and thrombotic complications. Less frequently, cardiac complications such as atrial fibrillation are seen. In this case report, we discuss the various complications encountered during the hospital stay of a 61-year-old male following a laparoscopic converted to open colectomy procedure for the treatment of a colorectal mass. Following surgery, a surgical pathology report revealed a newly diagnosed stage 3b colorectal adenocarcinoma. Multiple abscesses in the abdominopelvic cavity were discovered on computed tomography (CT), revealing a major surgical site infectious process. These findings warranted emergent surgical intervention and placement of multiple Jackson-Pratt drains. Due to previously untreated carcinoma promoting a prothrombotic state, the patient developed numerous thrombotic complications such as segmental pulmonary embolism, superior mesenteric vein thrombosis, and superficial thrombophlebitis of the saphenous veins. He also developed new-onset paroxysmal atrial fibrillation secondary to postoperative pain, as well as bilateral pleural effusions. Here, we shed light on the mechanisms of development of such complications, as well as the management and methods for prevention.