Introduction We examined the perioperative outcomes of patients undergoing open, laparoscopic, or robotic colectomy for T4b colon cancer, as well as the clinical factors associated with conversion to an open approach and its consequences on perioperative and oncologic outcomes. Methods The National Cancer Database was queried for patients undergoing colectomy for cT4b colon cancer (2010-2016). Patients undergoing laparoscopic or robotic colectomy were matched using Propensity-Score analysis. Factors associated with conversion to an open approach were assessed using Logistic-regression multivariable-analysis (MVA). Results Colectomy for cT4b colon cancer was performed in 9030 patients (open: n = 6,543, robotic: n = 157, laparoscopic: n = 2330). In the propensity-matched groups, robotic approach had lower rate of conversion (12% vs 37%, P < .001), shorter hospital stays (5 vs 7-days, P = .02), and similar overall-survival (5-yr: 49% vs 39%, P = .16), compared to laparoscopic approach. Conversion to an open approach was noted in 801(32%) of the patients undergoing minimally invasive surgical colectomy (robotic n = 23(15%), laparoscopic n = 778(33%). Factors associated with lower rate of conversion on multivariable-analysis included recent year of surgery (95% CI: 0.88-.97), robotic approach (95% CI: 0.22-.56), and surgeries performed in Academic hospitals (95% CI: 0.65-.96). Conversion to an open approach was associated with higher rate of positive parenchymal margin (31% vs 25%, P = .001), higher rate of 30-day readmission (12% vs 9.5%, P = .04), and similar overall survival (5-yr: 32% vs 35%, P = .19), compared to those who had no conversion. Conclusion At the National level, patients undergoing colectomy for T4b colon cancer via a robotic approach had more favorable perioperative outcomes compared to laparoscopic approach. Conversion to an open approach did not compromise long term survival, despite being associated with higher rate of positive margins and readmissions rate.