Background Accurate assessment and management of pain in critically ill patients who are nonverbal or cognitively impaired is challenging. No widely accepted assessment tool is currently in place for assessing pain in these patients. Objectives To evaluate the effect of implementing a new pain assessment tool in a trauma/neurosurgery intensive care unit. Methods Staff and patient satisfaction questionnaires and retrospective chart reviews were used before and after implementation of the Nonverbal Pain Scale. The questionnaire responses, frequency of pain documentation, and amount of pain medication given were compared from before to after implementation. Results Most staff (78%) ranked the tool as easy to use. Implementation of the tool increased staff confidence in assessing pain in nonverbal, sedated patients (57% before vs 81% after implementation, P = .02) and increased the number of pain assessments documented by the nursing staff for noncommunicative patients per day in the intensive care unit (2.2 before vs 3.4 after, P = .02). Patients reported decreased retrospective pain ratings (8.5 before vs 7.2 after, P = .04) and a trend toward a decrease in the time required to receive pain medication (38% before vs 10% after requiring >5 minutes to receive medication, P = .06). Conclusions Implementation of the Nonverbal Pain Scale in a critical care setting improved patients' ratings of their pain experience, improved documentation by nurses, and increased nurses' confidence in assessing pain in nonverbal patients.