Objectives: The diagnosis of pain in patients with low consciousness is a major challenge in the intensive care unit (ICU). Therefore, the use of behavioral tools for pain assessment could be an effective tool to manage pain in this group of patients. The aim of this study was to determine the effects on pain management by nurses using a critical care pain observational tool in patients with a decreased level of consciousness. Methods: Our research used a before and after design to evaluate the ability of nurses to manage pain in patients with low consciousness. A total of 106 ICU nurses were included in the study. The study was divided into three phases: pre-implementation, implementation, and post-implementation. The researchers first observed the nurses management of pain in their patients; this was done three times using a checklist following tracheal suctioning and position change procedures. The nurses were then taught how to apply the critical-care pain observational tool (CPOT). Post-implementation of the tool, the researchers re-evaluated trained the nurses' pain management. Result: Performance scores after training improved with relation to the nurses diagnosis of pain, pharmacological and nonpharmacological actions, reassessment of pain, and re-relieving of any pain. However, use of the tool did not improve the recording of the patient's pain and the relief measures used. Conclusion: Use of the CPOT can increase nurse's sensitivity to pain in non-conscious patients and drive them to track and perform pain management.