Background Regular pain assessment can lead to decreased incidence of pain and shorter durations of mechanical ventilation and stays in the intensive care unit. Objectives To document knowledge and perceptions of pain assessment and management practices among Canadian intensive care unit nurses. Methods A self-administered questionnaire was mailed to 3753 intensive care unit nurses identified through the 12 Canadian provincial/territorial nursing associations responsible for professional regulation. Results A total of 842 nurses (24%) responded, and 802 surveys could be evaluated. Nurses were significantly less likely (P < .001) to use a pain assessment tool for patients unable to communicate (267 nurses, 33%) than for patients able to self-report (712 nurses, 89%). Significantly fewer respondents (P < .001) rated behavioral pain assessment tools as moderately to extremely important (595 nurses, 74%) compared with selfreport tools (703 nurses, 88%). Routine (>50% of the time) discussion of pain scores during nursing handover was reported by 492 nurses (61%), and targeting of analgesia to a pain score or other assessment parameters by physicians by 333 nurses (42%). Few nurses (n = 235; 29%) were aware of professional society guidelines for pain assessment and management. Routine use of a behavioral pain tool was associated with awareness of published guidelines (odds ratio, 2.5; 95% CI, 1.7-3.7) and clinical availability of the tool (odds ratio, 2.6; 95% CI, 1.6-4.3). Conclusions A substantial proportion of intensive care unit nurses did not use pain assessment tools for patients unable to communicate and were unaware of pain management guidelines published by professional societies.