Background: Caregivers are a valuable support for patients and an important source of information about patient health, particularly in older adults who are more likely to be frail or have cognitive impairment. We sought to determine whether a) differences exist between patient and caregiver assessments and b) these differences were associated with increased caregiver burden. Methods: 100 cancer patients, age ≥ 65, and their caregivers independently assessed patient function, comorbidities, nutrition, psychological status, social activity and social support. Caregiver Strain Index (CSI) was used to assess caregiver burden. Patient-caregiver assessments were compared using the Wilcoxon signed rank test. The relationship between caregiver burden and variables in which patient-caregiver assessment differed was determined using a linear regression model and adjustment for confounders was done. Results: Median patient age was 70, 70% had advanced disease, 62% were on chemotherapy. Patients reported a median of 2 comorbid conditions, no falls within 6 months, and 39% reported > 5% weight loss. Patients reported good function (median KPS 90 and Medical Outcomes Study (MOS)-physical function 67), independence with most instrumental activities of daily living (IADL) (median OARS-IADL 13), having good social support (median MOS-social support survey 92), and good mental health (median Mental Health Index 85). 75% of caregivers experienced some caregiver burden (mean CSI 3.1±3.2; 15% had high burden). Caregivers were more likely than patients themselves to rate patients as having poorer function [needing more help with IADLs (p = 0.008), lower KPS (p = 0.02), and lower MOS-physical function (p < 0.0001)], poorer mental health (p = 0.0002), but more social supports (p = 0.03). Only a difference in patient-caregiver assessment of a patient’s need for help with IADLs was associated with increased caregiver burden (p = 0.002). Conclusions: Patients and caregivers differ in their assessment of patient function, mental health, and social support. However, only differences in patient-caregiver reported need for help with IADLs were associated with increased caregiver burden.