The current longitudinal study examined patterns and predictors of parent-reported gender-typed play behavior in adopted boys and girls in lesbian, gay, and heterosexual 2-parent families, across early childhood ( Mage = 2.82 to 6.06 years). Specifically, using a sample of 181 couples ( 56 lesbian couples, 48 gay male couples, and 77 heterosexual couples), we examined parent reports of children's gendertyped play behavior on the Pre-School Activities Inventory ( PSAI; Golombok & Rust, 1993) at 3 time points ( mean age = 2.82 years at T1, 3.93 years at T2, and 6.06 years at T3). Family structure variables ( i.e., parents' gender and sexual orientation; children's gender and sibling status) were included as predictors. At T1, according to parent reports, children in lesbian-parent families had less gender-differentiated behavior ( boys were less masculine, girls were less feminine) than children in heterosexual- and gay-parent families, whereas the degree of gender differentiation did not differ between heterosexual-versus gay-parent families. Findings from a Common Fate Growth Model ( Ledermann & Macho, 2014) revealed that, regardless of family type, the parent-reported gender-typed behavior of boys, but not girls, significantly changed over time ( i. e., boys' behavior became more masculine). Our findings have implications for researchers who study gender development in children and adolescents, particularly those who are being raised by 2 mothers or 2 fathers.