One in six children entering school experiences developmental delay. Maternal mental health represents one of the earliest, modifiable influences in a child's life. The objective of the review was to evaluate the association between maternal mental health and school-age child development, and we hypothesized there would be a negative association. Five databases were searched (Embase, CINAHL, Eric, PsycInfo, Medline). Key journals and reference lists were hand-searched. Two reviewers assessed studies based on inclusion criteria: (1) the exposure was any form of maternal mental health occurring during pregnancy or postpartum periods; (2) the outcome was child development (>48 months to 8 years); (3) the study recruited participants from developed countries; and (4) publication was in English between January, 1990 and December, 2012. Disagreements were resolved by consensus. Study quality was assessed by two reviewers using the Scottish Intercollegiate Guideline Network and disagreements were resolved by consensus. Data extraction was conducted by one reviewer using standardized forms. Maternal mental health problems in pregnancy and/or the postpartum period increased the likelihood that school-age children experienced suboptimal global, behavioral, cognitive, and socio-emotional development. The findings highlight the need for maternal mental health assessment during the prenatal, postnatal, and early childhood periods.