This study aims to characterize the association between maternal pregnancy intention and socioemotional developmental outcomes in a Brazilian sample of preschool-aged children. Data from children aged 4 to 5 years and their primary caregivers in Embu das Artes, a Brazilian municipality in the state of São Paulo, were collected in 2016. Maternal pregnancy intention was defined as intended or unintended, which was then further stratified as mistimed or unwanted. Outcomes included socioemotional developmental delay, internalizing and externalizing behaviors, and school readiness. We estimated risk ratios (RRs) for unadjusted and inverse-probability-weighted regression adjustment (IPWRA) analyses using 2-level (intended vs unintended) and 3-level (intended vs mistimed vs unwanted) exposure definitions. Of 1,034 total mothers, 40.7% reported their pregnancy as intended, 46.0% as mistimed, and 13.4% as unwanted. In both unadjusted and IPWRA analyses comparing intended and unintended pregnancies, all associations failed to reach statistical significance. In the IPWRA analysis using the 3-level exposure definition, unwanted pregnancies were associated with higher risk of socioemotional developmental delay (RR = 1.14; 95% confidence interval CI, 1.01-1.28) and co-occurring internalizing and externalizing behaviors (RR = 1.11, 95% CI, 1.00-1.22), compared with intended pregnancies. There was higher risk of poor child outcomes among unwanted compared with intended pregnancies, whereas mistimed pregnancies were not associated with poor outcomes. Further research using standardized definitions of pregnancy intention along with targeted interventions that increase access to family planning services and counseling for parents of children born after unintended pregnancies is needed.