Evidence is mixed regarding the effects of hematopoietic cell transplantation (HCT) on changes in cognitive functioning among adults. Meta-analysis, which is designed to help reconcile conflicting findings, has not yet been conducted on studies of adults receiving HCT. To fill this gap, the current study provides a systematic review and meta-analysis of cognitive functioning in adults receiving HCT. A search of PubMed, PsycInfo, CINAHL, and Cochrane Library yielded 732 abstracts, which were independently evaluated by pairs of raters. Seventeen studies were systematically reviewed; 11 were retained for meta-analysis. There was agreement that cognitive impairments are evident for a subset of patients before HCT. Meta-analytical findings of 404 patients revealed no significant changes in cognitive functioning pre- to post HCT (P-values >0.05). Age, time since transplant and TBI were not associated with changes in cognitive functioning. Patients who received autologous transplants were more likely to demonstrate improvements in attention (P=0.004). The systematic review identified several limitations of existing literature, including small, clinically heterogeneous samples. Large, cooperative group studies are needed to address these design limitations. Nevertheless, results from the current meta-analysis suggest that cognitive functioning does not significantly change following HCT.Bone Marrow Transplantation advance online publication, 6 May 2013; doi:10.1038/bmt.2013.61.