BACKGROUND: Pharmacological interventions for sleep (analgesic, sedative and hypnotic agents) can both disrupt and induce sleep and have many negative side effects within the intensive care population. The use of complementary and alternative medicine therapies to assist with sleep has been studied but given the variety of modalities and methodological limitations no reliable conclusions have been drawn. OBJECTIVE: To synthesise research findings regarding the effectiveness of using complementary and alternative medicine interventions within the domains of mind and body practices (relaxation techniques, acupuncture) and natural biologically based products (herbs, vitamins, minerals, probiotics) on sleep quality and quantity in adult intensive care patients. REVIEW METHOD USED: Systematic review. DATA SOURCES: Five databases were searched in August 2018 and updated in February 2019 and 2020. REVIEW METHODS: Searches were limited to peer reviewed randomised controlled trials, published in English involving adult populations in intensive care units. Interventions were related to the complementary and alternative medicine domains of mind and body practices and natural products. Included studies were assessed using Cochrane's risk of bias tool. RESULTS: Seventeen studies were included. The interventions used varied: 4 investigated melatonin; 4 music +/- another therapy; 3 acupressure; 2 aromatherapy and 1 each for relaxation and imagery, reflexology, bright light exposure and inspiratory muscle training. Measurement of sleep quantity and quality was also varied: 5 studies used objective measures such as Polysomnography and Bispectral index with the remaining using subjective patient or clinician assessment (for example, Richards-Campbell Sleep Questionnaire, Pittsburgh Sleep Quality Index, observation). Given the different interventions, outcomes and measures used in the studies a meta-analysis was not possible. Generally, the results support the use of complementary and alternative medicine for assisting with sleep with 11 out of 17 trials reporting significant results for the interventions examined. CONCLUSIONS: Complementary and alternative medicine interventions, in particular, melatonin and music, have shown promise for improving sleep in adults with critical conditions; however, further research that addresses the limitations of small sample sizes and improved techniques for measuring sleep is needed.