Perimenopause is a transitional stage of reproductive aging characterized by fluctuating hormone levels which impact cognition. Cognitive concerns (e.g., forgetfulness, difficulty concentrating) are frequently reported during this stage and can affect daily functioning, work, and relationships. Numerous studies have reported that perimenopause is associated with subjective cognitive complaints and objective cognitive deficits; however, findings have been inconsistent due to methodological variability including different comparison groups (premenopause/postmenopause) and different outcomes investigated (attention, memory, etc.). This systematic review and meta-analytic investigation therefore sought to provide clarity by exploring differences in cognition during perimenopause compared to both premenopause and postmenopause. Across 26 articles comprising 9,428 participants, group differences were examined between perimenopausal and premenopausal women (21 studies), and between perimenopausal and postmenopausal women (21 studies). Overall, perimenopausal women exhibited poorer cognitive outcomes than premenopausal women (moderate effect), though, notably, this negative effect was only found in studies utilizing the Stages of Reproductive Aging Workshop (STRAW+10) criteria to categorize menopausal/reproductive stages. In contrast, no differences were found between perimenopausal and postmenopausal women, though moderator analyses indicated that studies not utilizing the STRAW+10 criteria yielded significant effects (better cognition in perimenopausal than postmenopausal groups). Additionally, compared to postmenopausal women, perimenopausal women demonstrated better objective cognitive outcomes (accuracy, reaction time), with a trend for poorer self-reported outcomes. These findings highlight the importance of applying standardized reproductive staging (STRAW+10) and the inclusion of subjective and objective assessments in future research. A clearer understanding of cognitive changes during perimenopause may improve clinical assessment and inform interventions to support cognitive health in midlife women. (PsycInfo Database Record (c) 2026 APA, all rights reserved).