This study investigated risk factors and impact of open conversion on outcomes of 207 consecutive patients who had laparoscopic resection of colorectal cancer at our institution. Conversion occurred in 15.9% of patients, mostly because of invasion to adjacent structures (30.3%), bulky tumor (21.2%), and adhesions (18.2%). Converted patients had significant larger tumor size, advanced stage, increased operative blood loss, time to walk independently, prolonged hospital stay, number of massive hemorrhage, ileus, anastomotic hemorrhage, abdominal hemorrhage, peritonitis/septic shock, and wound infection than completed laparoscopy patients. Factors associated with conversion were obesity [relative risk (RR)=6.92; 95% confidence interval (CI), 1.7-28.09], date of operation (RR=0.37; 95% CI, 0.15-0.95), advanced tumor stage (RR=7.67; 95% CI; 1.19-49.2), size (RR=1.97; 95% CI, 1.42-2.72), and rectum location (RR=2.73; 95% CI, 1.09-6.84). Converted patients had worse cumulative disease-free (P<0.001) and overall survival (P<0.001) than laparoscopic completed patients.