It is unclear if the intakes of different types of protein have changed over time. We delineated trends in types of protein (beef, pork, lamb or goat, chicken, turkey, fish, dairy, eggs, legumes, and nuts and seeds) in US children (2-<12 years) and adolescents (12-19 years) from 1999 to 2010. We used 6 repeated cross-sectional surveys (National Health and Nutrition Examination Survey 1999-2010, n≥1,665 for children; n≥1,156 for adolescents) to test for linear trends in the intake of types of protein (grams per kilogram of body weight) among children and adolescents, and according to sociodemographic groups and participation in food assistance programs. Among children, pork intake (0.76 to 0.51 g/kg) decreased, but chicken (0.98 to 1.28 g/kg), all poultry (1.18 to 1.55 g/kg), egg (0.63 to 0.69 g/kg), and legume (0.35 to 0.54 g/kg) intake increased (all P<0.05). Among adolescents, beef intake decreased (0.92 to 0.67 g/kg) whereas chicken (0.59 to 0.74 g/kg) and all poultry (0.72 to 0.86 g/kg) intake increased from 1999 to 2010 (all P<0.01). Participants of the Women, Infants, and Children (WIC) increased the intake of chicken and dairy (all P<0.05) over time whereas no significant trend was observed for income-eligible non-participants. Fish intake did not change in any age group, and recommended types of protein (poultry, fish, nuts and seeds) declined among children of lower socioeconomic status. Intake of recommended types of protein increased among children, adolescents and WIC participants. However, subgroup analyses suggest socioeconomic disparities.