This study aimed to examine: (1) patient–proxy agreement on executive functioning (EF) of patients with primary brain tumors, (2) the relationships between patient- and proxy-report with performance-based measures of EF, and (3) the potential influence of performance-based measures on the level of agreement.

Meningioma and low-grade glioma patients and their informal caregivers completed the Behavior Rating Inventory of Executive Function (BRIEF-A) 3 months after surgery. The two index scores of the BRIEF-A, Behavioral Regulation and Metacognition, were evaluated. Mean scores of patients and proxies were compared with normative values and with each other. Patient–proxy agreement was evaluated with Lin’s concordance correlation coefficients (CCCs) and Bland–Altman plots. Pearson correlation coefficients between reported EF and performance-based measures of EF were calculated. Multiple regression analysis was used to evaluate the potential influence of test performance on differences in dyadic reports.

A total of 47 dyads were included. Patients reported significantly more problems on the Metacognition Index compared to norms, and also in comparison with their proxies. Effect sizes indicated small differences. Moderate to substantial agreement was observed between patients and proxies, with CCCs of 0.57 and 0.61 for Metacognition and Behavioral Regulation, respectively. Correlations between reported EF and test performance ranged between −0.37 and 0.10. Dyadic agreement was not significantly influenced by test performance.

Patient–proxy agreement was found to be moderate. No clear associations were found between reported EF and test performance. Future studies should further explore the existing and new methods to assess everyday EF in brain tumor patients.