Staff in a tertiary hospital critical care unit in Doha, Qatar, suggested that the Critical-Care Pain Observation Tool (CPOT) would be a better tool for assessing pain in ventilated and sedated patients than current local practice. We undertook a rapid synthesis of evidence to establish whether current research supports use of CPOT for assessing pain in ventilated and sedated patients in a critical care setting. CPOT has been shown in reviews and more recent primary studies to be reliable and valid for most patients unable to self-report in critical care settings. This finding is supported by several guidelines. Studies also suggest that CPOT is feasible for use in research and clinical practice though training of observers is important. Further research may be warranted to strengthen current evidence, particularly in patients with neurological trauma.