Primary Objective: To investigate the level of agreement and differences regarding the perception of family functioning between patients with acquired brain injury and their partners. Our hypothesis was that patients would report better family functioning than their partners. Research Design: Cross-sectional study Methods and Procedures: Baseline data were used from 77 patient-partner dyads (87.0% stroke) who were participating in the ongoing CARE4Patient and CARE4Carer trials. Family functioning was assessed using the General Functioning subscale of the McMaster Family Assessment Device (FAD-GF). Agreement was assessed with intraclass correlation coefficient, a Bland-Altman plot, percentages absolute agreement and weighted kappa values. Differences were tested with Wilcoxon signed-rank tests. Main Outcomes and Results: Patients and their partners differed in their perception of family functioning. Within-dyad agreement was poor regarding the overall FAD-GF scores with partners reporting significantly poorer family functioning compared to the patients (32.5% versus 18.2%). Agreement regarding the individual items ranged from slight to moderate. Conclusions: Health care professionals should assess family functioning after stroke in both patients and their partners, and any discrepancies should be discussed with both members of the patient-partner dyad.