OBJECTIVES: Conversion to open surgery is an intra-operative outcome indicating failed to complete a planned minimally-invasive surgery (MIS). Conversion in rectal cancer resection is high yet the associated clinical and economic impacts of conversion are less understood. METHODS: Rectal cancer patients underwent rectal resection in Premier Hospital Perspective® Database were included. Conversion and surgical approaches were defined by ICD-9 . Multivariate regression was used to estimate the impacts of conversion through comparing converted vs. (1)non-converted cases; (2)open cases. Outcomes included postoperative complications, length of stay(LOS), operation-room time, and hospitalization cost. Stratification analyses were conducted by surgeon specialties and hospital teaching status. RESULTS: Among 25,814 rectal cancer patients with rectal resection, 33.4% were done with MIS and 22.8% of those MIS were converted to open surgery. Patients who converted to open surgery had significantly higher risk of postoperative complications(vs. non-converted: OR 1.47, 95%CI[1.29, 1.66]; vs. Open OR: 1.16 95%CI[1.04,1.29]), longer operation time (vs.non-converted: 21.26mins, 95%CI[ 6.15, 36.38]; vs. Open: 60.14mins, 95%CI[3.46,116.83]), and higher hospitalization cost (vs.non-converted: $2270.47, 95%CI[$11251.99, 3288.95]; vs. Open: $1942.48 95%CI[880.41, 3004.54]); LOS of converted cases is significantly longer than non-converted cases (0.85days, 95%CI[0.51-1.19]) after adjusted for covariates. Stratifying by community or teaching hospital, the converted cases in community hospital had significantly higher risk of postoperative complication, longer operation-room time and higher hospitalization cost compared with both non-converted and open cases; while in teaching hospital, the outcome differences between converted and open cases became insignificant. Similar results were found after stratification by non-colorectal or colorectal surgeon. CONCLUSIONS: Conversion to open surgery for rectal cancer resection is associated with higher risk of complications, longer LOS, operation-room time and higher hospitalization cost. The impacts of conversion vary in different types of surgeons and hospitals. Further research is warranted for prevention of conversion and how to tailor the prevention method to different archetypes of care providers.