Background: Estimating quality of life (QoL) in patients with breast cancer is of importance in assessing treatment outcomes. Adjuvant endocrine therapy is widely used for hormone receptor-positive (HR+) early-stage breast cancer (EBC), and evidence suggests that aromatase inhibitors (AIs) may improve QoL for these patients. This study evaluated QoL in postmenopausal Chinese patients with HR + EBC taking AIs. Methods: This was a prospective, multicenter, and observational study that had no intent to intervene in the current treatment of recruited patients. Eligible patients were recruited within 7 days of beginning adjuvant treatment with AIs. The Functional Assessment of Cancer Therapy-Breast (FACT-B) scale was used to evaluate the patients' QoL. Data were collected at baseline and at 6, 12, 18, and 24 months. Results: From June 2010 to October 2013, a total of 494 patients with HR+ EBC were recruited from 21 centers. There was a 7.51-point increase in the patients' mean FACT-B trial outcome index (TOI), from 90.69 at baseline to 98.72 at 24 months (P < .0001). The mean TOI scores at baseline, 6, 12, and 18 months were 90.69, 94.36, 97.71, and 96.75, respectively (P < .0001, for all). The mean (FACT-B) emotional well-being subscale scores at baseline, 6, 12, 18, and 24 months were 16.32, 16.55, 17.34 (P < .0001), 17.47 (P < .0001), and 17.85 (P < .0001), respectively, and social well-being scores were 18.61, 19.14 (P < .04), 19.35 (P < .008), 18.32, and 18.40, respectively. In the mixed model, baseline TOI, clinical visits, prior chemotherapies, age group, and axillary lymph-node dissection presented statistically significant effects on the change of FACT-B TOI and FACT-B SWB, whereas only baseline TOI, clinical visits, and prior chemotherapies presented statistically significant effects on the change of FACT-B EWB. FACT-B TOI, being the most pertinent and precise indicator of patient-reported QoL, demonstrated significant changes reflecting clinical benefit of adjuvant AIs endocrine therapy in the QoL of HR + EBC patients. Conclusions: The study demonstrated significant improvements in the long-term QoL of postmenopausal Chinese patients with HR+ EBC at 6, 12, 18, and 24 months after starting treatment with AIs. The current study indicates improved long-term QoL with AI adjuvant treatment, which will aid clinicians in optimizing treatment to yield effective healthcare outcomes.