Resumo. ABSTRACT For children with motor delays, the intervention effectiveness regarding children's routine, overall self-perceptions, and engagement in the lessons, have been understudied. Furthermore, specific sex differences still lack evidence. This study examines the effectiveness of mastery Climate (MC) motor intervention on girls' and boys' daily routine, motor performance, BMI, self-perceptions, and engagement, and the sex differences across these variables. Children with motor delays were randomly assigned to MC Group or Comparison Group. We assessed children's routine at home; perceived competence, social acceptance, and global self-worth; BMI; motor skills; and qualitative engagement in the lesson. Results show girls and boys increased the playtime, motor scores, perceptions of cognitive and motor competence, social acceptance, global self-worth, and engagement with success in the lessons; and, decreased TV time and free play, changing tasks, distraction, and conflicts in the lesson. In conclusion the MC intervention was effective in fostering girl's and boys' achievement.