Objective: This study aimed to evaluate self‐reported cognitive functioning of postmenopausal breast cancer patients before and during endocrine treatment compared with healthy female controls, and to investigate associations between self‐reported cognitive functioning, cognitive test performance and anxiety/depression, fatigue, and menopausal complaints. Methods: Self‐reported cognitive functioning, anxiety/depression, fatigue, menopausal complaints, and cognitive tests performance were assessed before (T1) and after 1 year (T2) of adjuvant endocrine treatment in postmenopausal chemotherapy‐naïve breast cancer patients. Self‐reported cognitive functioning was assessed by the cognitive failures questionnaire and interview questions concerning cognitive complaints. Patients participated in the TEAM‐trial, a prospective randomized study investigating tamoxifen versus exemestane as adjuvant therapy for hormone‐sensitive breast cancer. Identical information was obtained from healthy postmenopausal volunteers. Results: Two measures for self‐reported cognitive functioning provided the distinctive results. At T1 and T2, healthy controls reported a higher frequency of cognitive failures than patients; change over time did not differ between groups. The prevalence of cognitive complaints did not differ between the groups at T1, but change over time regarding attention/concentration complaints differed between groups, due to an increased prevalence in tamoxifen users. Self‐reported cognitive functioning showed moderate associations with anxiety/depression, fatigue, and menopausal complaints. Cognitive test performance was not associated with self‐reported cognitive functioning, but weakly with anxiety/depression and fatigue. Conclusion: Adjuvant therapy with tamoxifen and exemestane did not influence the self‐reported frequency of cognitive failures. Increased attention/concentration complaints were observed in tamoxifen users, but not in exemestane users. This latter finding should be confirmed with better validated instruments. Copyright © 2011 John Wiley & Sons, Ltd.