BACKGROUND:Self-care behaviors in people living with type 2 diabetes are important to achieving optimal glycemic control. Major depression in type 2 diabetes is associated with decreased adherence to self-care behaviors. The association between subthreshold depression and self-care behaviors, however, has not previously been systematically reviewed. The objective of this review is to determine the association between subthreshold depression and self-care behaviors. METHODS:A systematic search was performed in five electronic databases that included MEDLINE, EMBASE, PsycINFO, Emcare, and CINAHL. Any observational studies in adults with type 2 diabetes, investigating the association between subthreshold depression and any self-care behaviors, were included in the review. Qualitative studies, review articles, and gray literature were excluded. Two reviewers independently completed the title and abstract and full-text screening, appraised the study quality, and extracted the data. A third reviewer resolved any discrepancies between the reviewers if needed. Included articles were critically appraised using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist. Meta-analyses were not conducted because criteria for conducting such analyses were not met. RESULTS:A total of 6408 articles were identified through the database searching. After the abstract and full-text review, two articles met the inclusion criteria. One of the included study was cross-sectional while the other was a longitudinal study. Both studies showed inconsistent findings in the association between subthreshold depression and self-care behaviors. Important risks of bias were identified in the included studies. DISCUSSION:The evidence from the two included studies on a possible association between subthreshold depression and self-care behaviors in adults with type 2 diabetes was not consistent and potentially biased. Our review established a gap in knowledge and suggests that further high-quality studies are needed to examine the association between subthreshold depression and self-care behaviors in people with type 2 diabetes. SYSTEMATIC REVIEW REGISTRATION:PROSPERO CRD42018116373.