Little is known about the achievement of developmental milestones (i.e., COL) after pediatric liver transplantation. The aim of this study was to examine the COL of young adults who underwent a liver transplantation during childhood and to compare it to healthy peers. Furthermore, we studied factors possibly related to their COL. COL was assessed using the CLQ, which assesses the achievement of developmental milestones (autonomy, psychosexual, social, and antisocial development) and risk behavior (substance abuse and gambling). Sociodemographic characteristics and clinical data were collected using the prospective institutional liver transplantation database. A total of 39 young adults who underwent a liver transplantation at the UMCG in their childhood completed the CLQ. They achieved fewer milestones with regard to autonomy, psychosexual, and social development compared to healthy peers, and they reported less risk behavior. Neither age at the time of study nor age at the time of transplantation was significantly correlated with any of the COL subscales. Young adults show delay in reaching developmental milestones in every dimension after a liver transplantation during their childhood.