Hostility may confer a risk of cardiovascular disease and all-cause mortality, but why is uncertain. A common origin in suboptimal fetal and early postnatal life may lie beneath. This study tested whether prenatal and postnatal growth predicts hostility in adult life. Women (n = 939) and men (n = 740) born in Helsinki, Finland, from 1934 through 1944 filled out the Cook-Medley Hostility Scale at an average age of 63.4 years. Growth was estimated from birth, child welfare clinic, and school records. Adult body size was measured in a clinic. Men and women who had higher levels of hostility in adulthood were born lighter and thinner, showed slower weight gain from birth to 6 months of age, were lighter throughout childhood (standardized regression coefficients (beta) <-0.05; 95% confidence intervals (95% CI), -0.14 to -0.00; p values <.05), but were heavier in adulthood (beta values > 0.06; 95% CIs, 0.02-0.14; p values <.01). They were also shorter from 6 months until the age of 1 year (beta values <-0.09; 95% CIs, -0.14 to -0.03; p values <.003), and tended to be shorter in adulthood (beta = -0.05; 95% CI, -0.09 to 0.00; p = .06). The latter effects were largely attributable to slower growth in stature from birth to 6 months (beta = -0.08; 95% CI, -0.14 to -0.02; p = .005). The associations were not explained by major confounders. Our study suggests that slow prenatal and infant growth is linked with hostility in adult life.