Caregivers play a vital role in providing support to adults with a chronic condition, or cognitive or physical impairment. Low health literacy in caregivers has the potential to impact adequate care provision, and consequently, care recipient health outcomes. The aim of the study was to systematically review literature related to health literacy of caregivers of adult care recipients, and examine its relationship with care recipient, and caregiver, health outcomes. Electronic databases were searched for relevant English-language publications that assessed health literacy in caregivers. Included studies were abstracted into evidence tables and assessed using an eight-item quality scale. The search identified 2717 new titles and abstracts, with 67 shortlisted for full review. Twelve papers from 2003 to 2015 met the inclusion criteria. The prevalence of limited health literacy in caregivers ranged from 0% to 52.5% depending on the measure and cut-off criteria used. Associations were found between low caregiver health literacy and (i) poorer care recipient self-management behaviours; (ii) increased care recipient use of health services; and (iii) increased caregiver burden. The quality of the studies ranged from fair to excellent. Low health literacy in caregivers differed depending on the measures and scoring criteria used. Evidence to support the relationship between caregiver health literacy and care recipient, and caregiver health outcomes was limited to single studies. Recommendations for further research include: the development of caregiver health literacy measures across different populations; examination of associations between caregiver health literacy and care recipient outcomes; and the development of interventions designed to improve caregiver health literacy.