BACKGROUND: Deprescribing is a strategy to optimize medication use and to prevent medication harm. Despite the fact that behavioral theories have been shown to be useful in explaining health behaviors, the literature on deprescribing relies almost exclusively on attitudes as an explanatory factor for deprescribing behavior. This study systematically reviews the literature that made explicit use of the constructs included in health behavior theories (HBTs) to explain older adults' and informal caregivers' deprescribing behavior and outcomes. METHODS: Studies were screened from five electronic databases by two reviewers. Quantitative interventional and non-interventional studies applying at least one HBTs or construct from these theories to older adults' or informal caregiver' intention or behavior to deprescribe, were included. Studies that used the patients' attitudes toward deprescribing (PATD) questionnaire or its revised version were excluded. RESULTS: A total of 11 non-interventional studies and 11 interventional studies were identified, seven of which applied HBTs, and the other 15 used constructs from the HBTs. Health literacy and locus of control were identified as moderator variables. Only two studies targeted informal caregivers' deprescribing intentions or behavior. CONCLUSIONS: HBTs are not systematically used. However, combining the main HBT constructs reported in the literature offers a better explanation of the (intention to) engage in deprescribing. TRAIL REGISTRATION: The study protocol (ID: CRD42022378157) was published on PROSPERO.