We conducted a randomized clinical trial evaluating the efficacy of a cognitive rehabilitation (CR) intervention compared with a wait list (WL) control condition on cognitive complaints, neuropsychological and brain functioning in breast cancer survivors (BCS).The small group intervention of five sessions included psychoeducation and cognitive exercises.Disease-free BCS with cognitive complaints, diagnosed with stage I, II or III breast cancer, completed primary treatment 18 months to 5 years earlier. Neurocognitive test data and cognitive complaints on the Patient's Assessment of Own Functioning Inventory (PAOFI) were assessed at baseline (T1), immediately post-intervention (T2), and 2 months later (T3). A subgroup of participants underwent resting state quantitative electroencephalography (qEEG) at all three assessment time points.Forty-eight participants [mean age (SD) 53.8 (8.2)] completed T1 assessments, and 29 participants had analyzable qEEG data. The CR group improved significantly over time compared with the WL group on PAOFI total and memory scores (both p = .01) and on Rey Auditory Verbal Learning Test (RAVLT) total (trials I-V) (p = .02) and RAVLT delayed recall (p = .007) scores. On qEEG, the CR group showed a significant decrease in delta 'slow wave' power (p = .02) and an increase in the frontal distribution of alpha power (p = .04) from T1 to T2.BCS in the CR group showed immediate and sustained improvements in self-reported cognitive complaints and memory functioning on neurocognitive testing. Results of the qEEG substudy provide some support for neurophysiological changes underlying the intervention. Copyright © 2015 John Wiley & Sons, Ltd.