Background Sleep disturbances are highly prevalent among patients admitted to the Intensive Care Unit (ICU), significantly impacting their recovery and psychological well-being. Complementary and holistic nursing interventions such as aromatherapy, music therapy, guided imagery, and foot massage have been proposed as non-pharmacological strategies to improve sleep quality. Objective To systematically review existing literature on the effectiveness of complementary and holistic nursing therapies in improving sleep quality among adult ICU patients. Methods This systematic review followed the PRISMA 2020 guidelines. Literature searches were conducted in the EBSCOhost and Medline databases for studies published between 2013 and 2022 using the keywords: "complementary therapy," "holistic nursing," "ICU," and "sleep quality." Inclusion criteria were experimental studies focusing on ICU patients receiving complementary interventions aimed at improving sleep quality. The methodological quality of included studies was assessed using the Critical Appraisal Skills Programme (CASP). Results From 590 initially identified articles, five studies met the inclusion criteria, encompassing 164 participants in the intervention group and 166 in the control group. Interventions included aromatherapy, foot massage, Quranic recitation (Murottal), and interactive music therapy. Most studies reported statistically significant improvements in sleep quality metrics post-intervention. However, variations in study designs, sample sizes, and outcome measures limited the comparability across studies. Discussion Complementary nursing interventions …