ABSTRACT Objective Patients with cancer often undergo multiple extended treatments that decrease their quality of life. However, the quality of life of women with breast cancer after they undergo treatment remains underexplored in Brazil. Therefore, this study determined sociodemographic, behavioral, and clinical factors related to the post-treatment quality of life of women with breast cancer. Methods This cross-sectional study involved 101 women diagnosed with breast cancer between 2014 and 2016 and treated at a Brazilian Oncology Reference Service. Data were collected from them using face-to-face surveys. Quality of life was evaluated using the European Organization for the Research and Treatment of Cancer Core Quality of Life questionnaire (EORTC QLQ-C30) and EORTC Breast Cancer-specific Quality of Life questionnaire (EORTC QLQ-BR23). The data collected were analyzed using Student’s t-test and Mann-Whitney U test. Results The median score on the global health, functional, and symptom scales of the EORTC QLQ-C30 was 75.00 (Interquartile range=33.33), 75.99 (Standard deviation [SD]=19.26), and 19.67 (SD=16.91), respectively. The mean score on the functional and symptom scales of the EORTC QLQ-BR23 was 61.89 (SD=17.21) and 20.12 (SD=16.94), respectively. Furthermore, higher post-treatment quality of life was found to be associated with being aged 50 or more, being Black, having eight or more years of education, having a partner, having a paying job, receiving treatment from the private healthcare system, having a higher income, living in the municipality where healthcare services are availed, engaging in physical activity, not smoking, being more religious, having more social support, not being overweight, having no comorbidities, and undergoing lumpectomy. Conclusion Sociodemographic, behavioral, and clinical factors significantly impact the quality of life of women who undergo breast cancer treatment. Implementing interventions that improve health and reducing inequalities in the access to healthcare services can improve the quality of life of these patients. However Brazil Therefore sociodemographic behavioral posttreatment post crosssectional cross sectional 10 201 Service facetoface face surveys QLQC30 QLQC QLQ C30 C Cancerspecific specific QLQBR23. QLQBR23 QLQBR BR23 . BR QLQ-BR23) Students Student s ttest t test MannWhitney Mann Whitney QLQ-C3 7500 75 00 75.0 Interquartile range=33.33, range3333 range range=33.33 , 33 range=33.33) 7599 99 75.9 Standard SD=19.26, SD1926 SD =19.26 19 26 [SD]=19.26) 1967 67 19.6 SD=16.91, SD1691 SD=16.91 16 91 (SD=16.91) respectively QLQ-BR2 6189 61 89 61.8 SD=17.21 SD1721 17 21 (SD=17.21 2012 20 12 20.1 SD=16.94, SD1694 SD=16.94 94 (SD=16.94) Furthermore 5 Black education partner job system income availed activity smoking religious support overweight comorbidities lumpectomy Sociodemographic patients 1 QLQC3 C3 QLQBR2 BR2 QLQ-C 750 7 0 75. range333 range=33.3 3 759 9 SD=19.26 SD192 1926 =19.2 2 [SD]=19.26 196 6 19. SD169 SD=16.9 (SD=16.91 QLQ-BR 618 8 61. SD=17.2 SD172 (SD=17.2 20. (SD=16.94 range33 range=33. SD=19.2 SD19 192 =19. [SD]=19.2 SD16 SD=16. (SD=16.9 SD=17. SD17 (SD=17. range3 range=33 SD=19. SD1 =19 [SD]=19. SD=16 (SD=16. SD=17 (SD=17 range=3 SD=19 =1 [SD]=19 SD=1 (SD=16 (SD=1 range= = [SD]=1 SD= (SD= [SD]= (SD [SD] [SD