Purpose: It has been theorized that colonoscopy in patients presenting emergently with large bowel obstructions (LBO) secondary to colorectal cancer increases the risks of severe caecal dilatation, necrosis, perforation, and total colectomy. However, there is a gap in the evidence supporting this theory. Methodology: We conducted a retrospective cohort study of patients at a single tertiary institution with colorectal cancer requiring operation at their index admission using a 5-year database of colorectal cancer patients. Results: The database showed a total of 361 patients, 54 (15%) of these were emergency admissions requiring operation at their index admission. Twenty-four (44%) of these emergent patients presented with acute LBO. The mean caecal diameter of those with LBO was 83.2mm compared with 48.4mm of those not obstructed (p<0.05). 7/24 (30%) emergency patients with acute LBO underwent colonoscopy or flexible sigmoidoscopy prior to resection, with only one patient requiring subtotal colectomy due to caecal dilatation related to colonoscopy. The remaining 6 patients had treatment altered based on the results of their colonoscopy. Four patients had confirmation of cancer and thus proceeding to operative management, one patient had failure to arrest bleeding and proceeding to operative management, one patient had a rectal stent which then perforated and proceeded to operative management. Conclusion: In the correctly chosen patient population, it is safe to undergo diagnostic colonoscopy in patients presenting emergently with acute LBO due to colorectal cancer.