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 two-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 gender-typed play behavior on the Pre-School Activities Inventory (PSAI; Golombok & Rust, 1993) at three 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 two mothers or two fathers.