Purpose: Motor skill interventions are effective for improving young children’s fundamental motor skills, but less is known regarding if boys and girls equally benefit from these interventions. The purpose of this study was to compare changes in preschool-aged boys’ and girls’ fundamental motor skills across an intervention. Methods: Sixty-eight children (M_age = 4.4 years, SD = 0.44) participated in the study and completed the Test of Gross Motor Development 2nd Edition before and after a 600-minute Children’s Health Activity Motor Program (CHAMP) intervention. All girls’ (n = 27) and a random subsample of boys’ (n = 27) total, locomotor subtest, object control skill subtests, and individual skills were compared before (pre) and after (post) CHAMP. Potential sex differences in treatment effects were examined by sex by treatment interactions from repeated measures ANOVA, and potential sex differences in individual skills before, after, and across (change) were examined using MANOVAs. Results: Boys and girls had similar motor skills before and after the intervention. Boys and girls had higher scores at posttest, and CHAMP was equally effective for boys and girls. Boys outperformed girls on the run and kick (p < .05) at posttest. Conclusion: Findings support that CHAMP improves skills for both preschool boys and girls.