The aim of the present study was to describe socioeconomic inequalities in low birth weight (LBW), premature birth (PM) and small size for gestational age at birth (SGA) between 2000 and 2005 in Barcelona, Spain, jointly evaluating the effect of mother’s country of origin, and neighborhood of residence socioeconomic level measured using unemployment and educational level. We performed a cross-sectional study of births to mothers aged 12–49 years who were residents in the city of Barcelona in 2000–2005, analyzing adverse pregnancy outcomes (n = 61,676). Weighted multilevel logistic regression models were fitted with individual data on level 1 and neighborhood data on level 2, to obtain adjusted odds ratios (aOR) with 95% confidence intervals and residual variance. Individually, pregnancy outcomes are more favorable in births to older mothers and to mothers from Maghrib and Central and South America than from developed countries (including Spain) or from other developing countries. After adjusting for individual variables, poor pregnancy outcomes were associated with poor neighborhoods (more unemployment was associated to LBW: aOR = 1.56; PM aOR = 1.51; SGA aOR = 1.66). The same trend was observed for associations with illiteracy rate. The present study shows that there are socioeconomic inequalities in adverse pregnancy outcomes in the city of Barcelona. One of the main challenges in perinatal health continues to be the reduction of adverse pregnancy outcomes in the city.