ImportanceHigher lymphedema rates after axillary lymph node dissection (ALND) have been found in Black and Hispanic women; however, there is poor correlation between subjective symptoms, quality of life (QOL), and measured lymphedema. Additionally, racial and ethnic differences in QOL have been understudied.ObjectiveTo evaluate the association of race and ethnicity with long-term QOL in patients with breast cancer treated with ALND.Design, Setting, and ParticipantsThis cohort study enrolled women aged 18 years and older with breast cancer who underwent unilateral ALND at a tertiary cancer center between November 2016 and March 2020. Preoperatively and at 6-month intervals, arm volume was measured by perometer and QOL was assessed using the Upper Limb Lymphedema-27 (ULL-27) questionnaire, a validated tool for assessing lymphedema that evaluates how arm symptoms affect physical, psychological, and social functioning. Data were analyzed from November 2016 to October 2023.ExposuresBreast surgery and unilateral ALND in the primary setting or after sentinel lymph node biopsy.Main Outcomes and MeasuresScores in each domain of the ULL-27 were compared by race and ethnicity. Factors impacting QOL were identified using multivariable regression analyses.ResultsThe study included 281 women (median [IQR] age, 48 [41-58] years) with breast cancer who underwent unilateral ALND and had at least 6 months of follow-up. Of these, 30 patients (11%) self-identified as Asian individuals, 57 (20%) as Black individuals, 23 (8%) as Hispanic individuals, and 162 (58%) as White individuals; 9 individuals (3%) who did not identify as part of a particular group or who were missing race and ethnicity data were categorized as having unknown race and ethnicity. Median (IQR) follow-up was 2.97 (1.96-3.67) years. The overall 2-year lymphedema rate was 20% and was higher among Black (31%) and Hispanic (27%) women compared with Asian (15%) and White (17%) women (P = .04). Subjective arm swelling was more common among Asian (57%), Black (70%), and Hispanic (87%) women than White (44%) women (P < .001), and lower physical QOL scores were reported by racial and ethnic minority women at nearly every follow-up. For example, at 24 months, median QOL scores were 87, 79, and 80 for Asian, Black, and Hispanic women compared with 92 for White women (P = .003). On multivariable analysis, Asian race (β = –5.7; 95% CI, −9.5 to −1.8), Hispanic ethnicity (β = –10.0; 95% CI, −15.0 to −5.2), and having Medicaid (β = −5.4; 95% CI, −9.2 to −1.7) or Medicare insurance (β = −6.9; 95% CI, −10.0 to −3.4) were independently associated with worse physical QOL (all P < .001).Conclusions and RelevanceFindings of this cohort study suggest that Asian, Black, and Hispanic women experience more subjective arm swelling after unilateral ALND for breast cancer compared with White women. Black and Hispanic women had higher rates of objective lymphedema than their White counterparts. Both minority status and public medical insurance were associated with worse physical QOL. Understanding disparities in QOL after ALND is an unmet need and may enable targeted interventions to improve QOL for these patients.