Environmental factors, drugs, diet, and surgery alter the composition of the gut microbiota leading to the production of different metabolites or toxins that can cause disease or delay postoperative recovery. Surgical damage leads to gut barrier disruption, increased intestinal permeability, gut microbial imbalance, and immunologic compromise of the host with subsequent bacterial translocation from the gastrointestinal tract to systemic circulation. Therefore, perioperative stabilization of the intestinal microbiota is a potential method of reducing postoperative complication rates. Probiotics have been proposed as a viable option for prophylaxis of postoperative infections through increased intestinal motility to prevent bacterial overgrowth, improve gut barrier function, and modulate immune response. This review investigates microbial changes after surgery and the influence of probiotics on postoperative microbial composition. Infectious postoperative complications and immunologic changes related to probiotics/synbiotics were also reviewed in patients who underwent abdominal surgery.