Background Height is regarded as a marker of early-life illness, adversity, nutrition and psychosocial stress, but the extent to which differences in height are determined by early-life socioeconomic circumstances, particularly in contemporary populations, is unclear. This study examined socioeconomic differences in children's height trajectories from birth through to 21 years of age in four European countries. Methods Data were from six prospective cohort studies-Generation XXI, Growing Up in Ireland (infant and child cohorts), Millennium Cohort Study, EPITeen and Cardiovascular Risk in Young Finns Study-comprising a total of 49 492 children with growth measured repeatedly from 1980 to 2014. We modelled differences in children's growth trajectories over time by maternal educational level using hierarchical models with fixed and random components for each cohort study. Results Across most cohorts at practically all ages, children from lower educated mothers were shorter on average. The gradient in height was consistently observed at 3 years of age with the difference in expected height between maternal education groups ranging between -0.55 and -1.53 cm for boys and -0.42 to -1.50 cm for girls across the different studies and widening across childhood. The height deficit persists into adolescence and early adulthood. By age 21, boys from primary educated maternal backgrounds lag the tertiary educated by -0.67 cm (Portugal) and -2.15 cm (Finland). The comparable figures for girls were -2.49 cm (Portugal) and -2.93 cm (Finland). Conclusions Significant differences in children's height by maternal education persist in modern child populations in Europe.