Objectives Gastrointestinal complications, like blockage, are among the most common oncological emergencies. We investigated whether individuals with cancer presenting at the emergency department (ED) with intestinal obstruction were triaged accurately, and we further evaluated the triage decisions’ effect on their ED treatment outcomes. Data Sources A retrospective review was completed on all available records of adult cancer patients who were admitted with intestinal obstruction to a tertiary referral hospital. Over 3 years, 46 cancer patients were admitted from the ED with a provisional diagnosis of intestinal obstruction, confirmed by radiological examination. More than half the patients were undertriaged, which often resulted in these patients experiencing a series of risky time delays in the ED. Patients were significantly delayed in reaching five treatment outcomes: first assessment with a physician, initiation of treatment, decision to admit, length of ED stay, and length of hospital stay. Conclusion The application of triage in practice was inconsistent, inaccurate, and had a significant negative impact on patient treatment outcomes. Implications for Nursing Practice The study results indicated the need to critically analyze current triage training and policies to increase their effectiveness. Improvement strategies are identified in the literature, and several are discussed. Involving triage nurses in this work is essential.