Background Agitation and delirium frequently occur in cognitively impaired older people. We conducted a systematic review with narrative synthesis of the literature aiming to assess effectiveness of complementary and alternative medicine (CAM) modalities to address these conditions. Methods Following preliminary search, we included 40 original researches on CAM treatment of delirium and agitation in older persons. Then, the quality of these studies was assessed using the Downs and Black Checklist and Quality Assessment Tool for Studies with Diverse Designs, and the effect sizes were calculated. We subsequently conducted a narrative synthesis of the main findings, including theory development, preliminary synthesis, exploration of relationships within and between studies, and assessment of synthesis robustness. Results Forty articles that met the inclusion criteria were analyzed. Sixteen of these were randomized controlled trials. One article specifically addressed CAM treatment of delirium in patients without dementia, and the remaining 39 articles described treatments of agitated older persons with dementia. Thirty‐five of the 40 included studies suggested that the investigated CAM therapies may ameliorate the severity of agitation and delirium. The physiological surrogates of agitation assessed in these studies included cortisol level, chromogranin A level, and heart rate variability. Very few of the studies systematically assessed safety issues, although no major adverse effects were reported. Conclusion Overall, the systematic review of the literature suggests that several CAM modalities are potentially beneficial in the treatment of agitation and delirium among older persons. We suggest that promising CAM modalities should be further explored through large‐scale randomized controlled trials in different clinical settings. Copyright © 2017 John Wiley & Sons, Ltd.