While considerable research has examined gender development in middle childhood, little longitudinal work has been conducted at this time to indicate whether, for example, youth who show more or less gender conformity at one point continue to do so later. The present study investigated the consistency of gender identity and preferences for gender-stereotypical toys, clothing, and same-gender peer preferences among groups of transgender youth (n = 158), their siblings (n = 79), and an unrelated group of cisgender youth (n = 128) from a mean age of 7.0 (range 3.0-10.9) to a mean age of 9.6 (range 5.1-12.0). Furthermore, 65.5% of the youth were girls, 69.7% were White, 72.8% grew up in households with an annual household income of $75,000 or more, and 89.9% of parents had a bachelor's degree or higher. Overall, we found a small-to-medium correlation over this 2.6-year span within each group, both across the composite of measures and most measures individually. Despite the moderate stability over time, we found a decrease in the composite and individual scores over this time span for girls and for transgender participants. Together these results suggested some stability in children's gender identity and preferences in middle childhood and that this was true regardless of whether the child's gender did or did not align with their sex assignment at birth.