Background Little is known about plasma apolipoprotein profiles in very preterm-born and term-born preschool children compared with the adult population. This is of particular interest because apolipoprotein composition might contribute to cardiometabolic outcome in later life. Methods and Results Children aged 5 to 7 years born at term or with <32 weeks of gestation were included. Apolipoprotein concentrations were measured in plasma collected after an overnight fast using multiple-reaction monitoring-based mass spectrometry. Twelve apolipoproteins were measured in 26 former term and 38 former very preterm infants. Key findings were confirmed by assessing apolipoprotein levels using antibody-based assays. Comparing children born term and preterm, apolipoprotein A-I, A- IV , C- II , and C- III were significantly higher in the latter group. Term-born children showed plasma levels of apolipoprotein C- II and C- III quantitatively similar to the adult range (Bruneck study). Hierarchical clustering analyses suggested that a higher proportion of apolipoprotein C- III and C- II reside on high-density lipoprotein particles in children than in adults given the marked correlations of apolipoprotein C- III and C- II with high-density lipoprotein cholesterol and apolipoprotein A-I in children but not adults. High-density lipoprotein cholesterol concentrations were similar in children and adults but the pattern of high-density lipoprotein cholesterol-associated apolipoproteins was different (lower apolipoprotein A-I and C-I but higher A- II , A- IV , and M). Conclusions Our study defines apolipoprotein profiles in preschoolers and reports potential effects of prematurity. Further large-scale studies are required to provide evidence whether this apolipoprotein signature of prematurity, including high apolipoprotein C- II and C- III levels, might translate into adverse cardiometabolic outcome in later life.