A novel case report of acute abdominal compartment syndrome (ACS) with respiratory and hemodynamic collapse during colonoscopy in a western lowland gorilla (Gorilla gorilla gorilla), notably, without colonic perforation is presented here. ACS is a rapidly progressive and sustained increase in intra-abdominal pressure leading to shock with multisystem organ failure. Surgical intervention was mandatory, and abdominal decompression was immediately life-saving, although the patient died 1 wk later of surgical complications. Colonoscopy is a widely performed procedure that is generally considered safe, and serious complications during colonoscopy are rare. ACS has been previously reported during colonoscopy with perforation in four cases (human)^1,4,6,8. In this instance there was no evidence of perforation, representing not only a rare complication of the procedure, but also a novel cause of ACS. This is the first report of ACS in a nonhuman primate and of nonperforation-associated ACS in human or nonhuman primates.