OBJECTIVES: This study aimed to assess the impact of conversion from minimally invasive surgery (MIS) to open surgery in rectal resection for non-rectal cancer patients. METHODS: Patients who underwent rectal resection in Premier Hospital Perspective® Database from 2008/01 to 2015/09 were included. Cases with rectal cancer ICD-9 diagnosis codes were excluded. Conversions were identified by ICD-9. Multivariate regressions were used to estimate the impacts of conversion through comparing converted vs. 1)non-converted cases; 2)open cases. Outcome measurements included postoperative complications, length of stay(LOS), operation time, total hospitalization cost. Further stratification analyses by surgeon specialty and teaching status were performed. RESULTS: Among 20385 non-rectal cancer patients with rectal resection in the study, 33.8% were done with MIS and 23.5% of those MIS were converted to open procedure. For non-rectal cancer patients, conversion to open surgery had significant higher odds of postoperative complications(OR1.41, 95%CI[1.23-1.62]), longer LOS(0.89days, 95%CI[0.56-1.22]) and operation time(50.70mins, 95%CI[27.04-74.35]), higher total cost($2546.14, 95%CI[1503.10,3589.19]) than non-converted cases. Comparable LOS and total costs were observed among converted and open cases, but converted cases were associated with significantly higher risk of postoperative complications(OR1.13, 95%CI[1.01-1.28]), and longer operation time(71.22mins, 95%CI[48.43-94.02]). Among cases performed by non-colorectal surgeons, odds of having postoperative complications were significantly higher in the converted cases than non-converted cases(OR1.51, 95%CI[1.27, 1.79]) and open cases(OR1.15, 95%CI[1.00, 1.32]). In contrast, the impact of conversion on postoperative complication among colorectal surgeons’ cases was insignificant. In community hospitals, total hospitalization cost for converted cases was significantly higher than open cases ($2300.05, 95% CI[1131.05,3470.86] ); whereas in teaching hospitals, cost for converted cases were lower yet insignificant than open cases. CONCLUSIONS: Conversion of rectal resection among non-rectal cancer patients is associated with higher risk of complication and longer OR time than non-converted cases and open cases. There are variations among surgeon specialties and hospital teaching status.