Background <p>The safety of opioids in undifferentiated abdominal pain is well-established, yet concerns persist regarding nonsteroidal anti-inflammatory drugs. Specifically, theoretical risks suggest that the potent anti-inflammatory properties of ketorolac may blunt peritoneal signs, potentially masking surgical emergencies. This study evaluated whether initial analgesic selection (ketorolac versus morphine) influenced severe adverse outcomes requiring admission or invasive intervention in patients discharged from the emergency department with non-traumatic abdominal pain.</p> Methods <p>A retrospective cohort study analyzed 18,428 adults treated at a tertiary center in Taiwan (2021–2023). To isolate true analgesic effects and minimize confounding by indication, strict exclusions restricted the analysis to a highly selected subpopulation with uncomplicated abdominal pain. Patients received either ketorolac (<i>n</i> = 16,097) or morphine (<i>n</i> = 2331) and were discharged. The primary outcome was hospital admission or invasive intervention during a 72-h unscheduled return visit. Inverse probability of treatment weighting (IPTW) was applied to adjust for confounding variables.</p> Results <p>Ketorolac use was not associated with increased odds of 72-h hospitalization (adjusted odds ratio [AOR] 0.88; 95% confidence interval [CI] 0.58–1.33) or invasive intervention (AOR 1.16; 95% CI 0.69–1.97) upon return. Secondary analyses among readmitted patients demonstrated that ketorolac use was not associated with prolonged hospital length of stay; however, it was statistically associated with higher total medical costs compared to morphine.</p> Conclusions <p>Ketorolac was not associated with increased aggregate adverse outcomes compared to morphine in patients discharged with non-traumatic abdominal pain, suggesting it may be a viable opioid-sparing alternative in non-critically unwell patients.</p>