Aims Cognitive impairment occurs often in patients with chronic heart failure (CHF) and may contribute to sub‐optimal self‐care. This study aimed to test the impact of cognitive impairment on self‐care. Methods and Results In 93 consecutive patients hospitalized with CHF, self‐care (Self‐Care of Heart Failure Index) was assessed. Multiple regression analysis was used to test a model of variables hypothesized to predict self‐care maintenance, management, and confidence. Variables in the model were mild cognitive impairment (MCI; Mini‐Mental State Exam and Montreal Cognitive Assessment), depressive symptoms (Cardiac Depression Scale), age, gender, social isolation, education level, new diagnosis, and co‐morbid illnesses. Sixty‐eight patients (75%) were coded as having MCI and had significantly lower self‐care management (η2= 0.07, P < 0.01) and self‐confidence scores (η2= 0.05, P < 0.05). In multivariate analysis, MCI, co‐morbidity index, and NYHA class III or IV explained 20% of the variance in self‐care management (P < 0.01); MCI made the largest contribution explaining 9% of the variance. Increasing age and symptoms of depression explained 13% of the variance in self‐care confidence scores (P < 0.01). Conclusion Cognitive impairment, a hidden co‐morbidity, may impede patients' ability to make appropriate self‐care decisions. Screening for MCI may alert health professionals to those at greater risk of failed self‐care.