Background: Few studies have investigated the relationship between physician and patient-assessed performance status (PS) in blood cancers. Methods: Retrospective analysis among 1418 patients with haematologic malignancies seen at Dana-Farber Cancer Institute between 2007 and 2014. We analysed physician-patient agreement of Eastern Cooperative Oncology Group PS using weighted kappa-statistics and survival analysis. Results: Mean age was 58.6 years and average follow-up was 38 months. Agreement in PS was fair/moderate (weighted kappa = 0.41, 95% CI 0.37-0.44). Physicians assigned a better functional status (lower score) than patients (mean 0.60 vs 0.81), particularly when patients were young and the disease was aggressive. Both scores independently predicted survival, but physician scores were more accurate. Disagreements in score were associated with poorer survival when physicians rated PS better than patients, and were modified by age, sex and severity of disease. Conclusions: Physician-patient disagreements in PS score are common and have prognostic significance.