Background: Certain nutrient supplements (nutraceuticals) may target neurobiological pathways perturbed in bipolar disorder (BD) such as inflammation, oxidative stress, and mitochondrial dysfunction. Nutraceuticals thus may have a potential role as adjunctive treatments for BD. Methods: A search of Embase via embase.com, PubMed via PubMed, Cumulated index to nursing and allied health literature (CINAHL) Complete via EBSCO, and Cochrane Central Register of Controlled Clinical Trials via cochranelibrary.com was conducted to identify published randomized controlled trials assessing the efficacy of nutraceuticals on mood symptomatology in adults with BD. Search terms for BD, nutraceuticals, and clinical trials (total search terms = 75) were used to search from inception to February 20, 2020. The Cochrane Collaboration’s tool for assessing the risk of bias in randomized trials was used to assess the risk of bias. Results: A total of 1,712 studies were identified through the search. After rigorous screening, 22 studies were included in the review. There was large variability across the studies with 15 different nutraceutical agents assessed and as such insufficient homogeneity for a meta-analysis to be conducted (I2 > 50%). Studies revealed promising, albeit conflicting, evidence for omega-3 fatty acids and N-acetylcysteine. Isolated positive results were reported for coenzyme Q10. Conclusion: Given nutraceuticals are tolerable and accessible, they may be useful as potential adjunctive treatments for BD. Nutraceuticals targeting neuroinflammation or mitochondrial activity may have the most potential for the depressive phase. However, further studies are required to determine efficacy.