Background: Ipilimumab is an effective medication in advanced melanoma but can cause severe diarrhea and colitis. This study identified the rate of ipilimumab-induced diarrhea/colitis at the Juravinski Cancer Centre (JCC), its associated factors for development, overall survival (OS) and progression free survival (PFS). Methods: The Ontario Patient Information System was used to retrospectively identify all melanoma patients at the JCC who were treated with ipilimumab 3 mg/kg IV every 3 weeks (September 2012 to June 2016). Patient demographics, medical history, prior melanoma treatments, diagnosis of ipilimumab-induced diarrhea/colitis, interventions to treat the diarrhea/colitis, and OS and PFS were collected. Descriptive statistics summarized characteristics and outcomes. Kaplan-Meier methods estimated time to event outcomes. Cox regression evaluated whether markers were prognostic for time to diarrhea/colitis diagnosis. Results: 71 patients were treated with ipilimumab at the JCC, of which 22 patients (31%) developed diarrhea/colitis of any Grade; 4 patients developed Grade 1, 5 patients Grade 2, 6 patients Grade 3, 3 patients Grade 4, and 4 patients had unclear Grade. 11 patients required prednisone 1-2 mg/kg and 2 patients required anti-TNF treatment to treat their diarrhea/colitis; 1 patient required colectomy due to perforation. 10 patients required treatment discontinuation due to diarrhea/colitis. Whole cohort median OS and PFS was 340 days (95% CI 205, 519) and 110 days (95% CI 91, 138), respectively. Univariate analysis showed that only inadequate hematologic function at time of first ipilimumab application was prognostic of diarrhea/colitis (HR = 6.42, 95% CI 1.44, 28.62; p = 0.015). Conclusions: Our OS, PFS, and rate of all grade ipilimumab-induced diarrhea/colitis are similar to published data, however our rate of Grade > 2 is larger. Additional work is needed to identify risk factors for the development of this immune related adverse event.