We explored the relationships among patients’ and family members’ (FMs) health literacy, heart failure (HF) knowledge, and self-care behaviors using baseline data from HF patients and their FMs (N = 113 pairs) in a trial of a self-care intervention. Measures included Rapid Estimate of Adult Literacy in Medicine, Atlanta HF Knowledge Test, a heart failure Medication Adherence Scale, and sodium intake (24-hr urine and 3-day food record). Patients with low health literacy (LHL) were more likely to have lower HF knowledge (p < .001) and trended to poorer medication adherence (p = .077) and higher sodium intake (p = .072). When FMs had LHL, FMs were more likely to have lower HF knowledge (p = .001) and patients trended toward higher sodium intake (p = .067). When both patients and FMs had LHL, lowest HF knowledge and poorest medication adherence were observed (p < .027). The health literacy of both patient and FM needs to be considered when designing interventions to foster self-care.