Both preterm birth and early institutional deprivation are associated with neurodevelopmental impairment - with both shared and distinctive features. To explore shared underlying mechanisms, this study directly compared the effects of these putative risk factors on temperament profiles in six-year-olds: Children born very preterm (<32 weeks gestation) or at very low birthweight (<1500 g) from the Bavarian Longitudinal Study (n = 299); and children who experienced >6 months of deprivation in Romanian institutions from the English and Romanian Adoptees Study (n = 101). The former were compared with 311 healthy term born controls and the latter with 52 nondeprived adoptees. At 6 years, temperament was assessed via parent reports across 5 dimensions: effortful control, activity, shyness, emotionality, and sociability. Very preterm/very low birthweight and postinstitutionalized children showed similarly aberrant profiles in terms of lower effortful control, preterm = -0.50, 95% CI [-0.67, -0.33]; postinstitutionalized = -0.48, 95% CI [-0.82, -0.14], compared with their respective controls. Additionally, postinstitutionalized children showed higher activity, whereas very preterm/very low birthweight children showed lower shyness. Preterm birth and early institutionalization are similarly associated with poorer effortful control, which might contribute to long-term vulnerability. More research is needed to examine temperamental processes as common mediators of negative long-term outcomes following early adversity.