Background. The possible negative effects of smoking on postoperative outcomes have not been well studied in cancer patients. Methods. We used the VA Surgical Quality Improvement Program (VASQIP) database for the years 2002-2008, which assesses preoperative risk factors and postoperative outcomes for patients undergoing major surgery within the VA healthcare system. Results. Compared with never smokers, prior smokers and current smokers with GI malignancies were significantly more likely to have surgical site infection (SSI) (odds ratio [OR], 1.25; 95% confidence interval [95% CI], 1.09-1.44) (OR, 1.20; 95% CI, 1.05-1.38), combined pulmonary complications (combined pulmonary outcome [CPO]: pneumonia, failure to wean from ventilator, reintubation) (OR, 1.60; 95% CI, 1.38-1.87) (OR, 1.96; 95% CI, 1.68-2.29), and return to the operating room (OR, 1.20; 95% CI, 1.03-1.39) (OR, 1.31; 95% CI, 1.13-1.53), respectively. Both prior and current smokers had a significantly higher mortality at 30 days (OR, 1.50; 95% CI, 1.19-1.89) (OR, 1.41; 95% CI, 1.08-1.82) and 1 year (OR, 1.22; 95% CI, 1.08-1.38) (OR, 1.62; 95% CI, 1.43-1.85). Thoracic surgery patients who were current smokers were more likely to develop CPO (OR, 1.62; 95% CI, 1.25-2.11) and mortality within 1 year (OR, 1.50; 95% CI, 1.17-1.92) compared with nonsmokers, but SSI rates were not affected by smoking status. Current smokers had a significant increase in postsurgical length of stay (overall 4.3% [P<.001], GI 4.7% [P = .003], thoracic 9.0% [P<.001]) compared with prior smokers. Conclusions. Prior and current smoking status is a significant risk factor for major postoperative complications and mortality following GI cancer and thoracic operations in veterans. Smoking cessation should be encouraged prior to all major cancer surgery in the VA population to decrease postoperative complications and length of stay. © Society of Surgical Oncology 2011.