IMPORTANCE: Empathy is an aspect of the patient-physician relationship that may be particularly important in patients with chronic pain. OBJECTIVE: To measure the association of physician empathy with pain, function, and health-related quality of life (HRQOL) among patients with chronic low back pain. DESIGN, SETTING, AND PARTICIPANTS: This cohort study included adult enrollees from the Pain Registry for Epidemiological, Clinical, and Interventional Studies and Innovation national pain research registry. Study dates were from April 1, 2016, to July 25, 2023, with up to 12 months of follow-up. EXPOSURE: Physician empathy was assessed with the Consultation and Relational Empathy measure and dichotomized to yield very empathic physician and slightly empathic physician groups. MAIN OUTCOMES AND MEASURES: Main outcomes were patient-reported pain, function, and HRQOL measured with a numerical rating scale for low back pain intensity, the Roland-Morris Disability Questionnaire for back-related disability, and the Patient-Reported Outcomes Measurement Information System for HRQOL deficits pertaining to anxiety, depression, fatigue, sleep disturbance, and pain interference. Data were collected at 5 quarterly encounters from registry enrollment through 12 months and analyzed with generalized estimating equations, including multivariable models to measure temporal trends and to adjust for baseline and longitudinal covariates. RESULTS: Among the 1470 patients, the mean (SD) age was 53.1 (13.2) years, and 1093 (74.4%) were female. Patients completed 5943 encounters in which multivariable analyses demonstrated that greater physician empathy was inversely associated with pain intensity (β = -0.014; 95% CI, -0.022 to -0.006; P < .001), back-related disability (β = -0.062; 95% CI, -0.085 to -0.040; P < .001), and HRQOL deficits on each measure (eg, pain interference: β = -0.080; 95% CI, -0.111 to -0.049; P < .001). Correspondingly, compared with the slightly empathic physician group, the very empathic physician group reported lower mean pain intensity (6.3; 95% CI, 6.1-6.5 vs 6.7; 95% CI, 6.5-6.9; P < .001), less mean back-related disability (14.9; 95% CI, 14.2-15.6 vs 16.8; 95% CI, 16.0-17.6; P < .001), and fewer HRQOL deficits on each measure (eg, fatigue: 57.3; 95% CI, 56.1-58.5 vs 60.4; 95% CI, 59.0-61.7; P < .001). All physician empathy group differences were clinically relevant, with Cohen d statistics ranging from 0.21 for pain intensity to 0.30 for back-related disability, fatigue, and pain interference. Physician empathy was associated with more favorable outcomes than non-pharmacological treatments, opioid therapy, and lumbar spine surgery. CONCLUSIONS AND RELEVANCE: In this cohort study of adult patients with chronic pain, physician empathy was associated with better outcomes over 12 months. Greater efforts to cultivate and improve physician empathy appear warranted.