An increasing number of transgender children—those who express a gender identity that is “opposite” their natal sex—are socially transitioning, or presenting as their gender identity in everyday life. This study asks whether these children differ from gender‐typical peers on basic gender development tasks. Three‐ to 5‐year‐old socially transitioned transgender children (n = 36) did not differ from controls matched on age and expressed gender (n = 36), or siblings of transgender and gender nonconforming children (n = 24) on gender preference, behavior, and belief measures. However, transgender children were less likely than both control groups to believe that their gender at birth matches their current gender, whereas both transgender children and siblings were less likely than controls to believe that other people's gender is stable.