Introduction: Sleep promotion in the Intensive Care Unit (ICU) should be a priority because interruptions may prevent patients from getting enough sleep. Inadequate sleep might lead to delirium, anxiety, increased hospital stays, and higher mortalities. Critical care nurses with good knowledge and attitude towards sleep promotion interventions benefit critically ill patients’ quality of care and life. Critical illness, pain, mechanical ventilation, surroundings, and nurses’ activity at night contribute to sleep disturbances in ICU patients. The aim of this study was to determine critical care nurses’ knowledge regarding the physiology of sleep, interventions to promote sleep,attitude towards sleep, and sleep promotion. Methods: A cross-sectional study with a self-administered questionnaire and purposive sampling method was conducted among 109 critical care nurses at the ICU of a teaching hospital. Results: The mean score knowledge of critical care nurses was 4.72 (± 1.92), attitude towards sleep was 18.57 (± 3.56), and intervention towards sleep promotion was 70.00 (± 12.00). A significant correlation was observed between knowledge and attitude (p < 0.05, r = 0.22) and between attitude and intervention (p < 0.05, r = 0.32), indicating a modest correlation. Moreover, a significant association was noted between years of experience and attitude and intervention (p < 0.05). Conclusion: Critical care nurses’ knowledge, attitudes, and interventions were poor; hence, they need to improve their knowledge, attitude, and interventions. The significance of sleep promotion and factors leading to critical care nurses in Malaysia not promoting sleep among ICU patients needs to be rectified.