Background and purpose: Mastery motivation makes important contributions to children’s competence and school readiness. Children with developmental delay need to learn challenging tasks, so understanding the characteristics of their mastery motivation and the factors associated with it might increase their engagement. The aims of this study were to examine the characteristics of mastery motivation in pre-schoolers with developmental delay, and, by intergroup and intragroup comparison, examine the associations between temperament and mastery motivation for pre-schoolers with developmental delay. Methods: Eighty-five child-caregiver dyads participated, with forty dyads in the developmental delay group and forty-five in the typical development group (age from 1.5 to 4.58 years). The Dimensions of Mastery Questionnaire was rated by caregivers to assess all children’s indicators of mastery motivation. cognitive/object, gross motor, social-interaction persistence with others, and expressive indicators of mastery of pleasure and negative emotions in reaction to challenges. The Early Children Behavior Questionnaire was completed by the caregivers to provide data on the children’s temperament, and cognitive ability was collected in the developmental delay group. Results: Children with developmental delay had lower levels of mastery motivation on most of the instrumental domains and indicators of the expressive aspect than conference group. They showed their strength on domains of gross motor, social interaction with adults, and mastery pleasure and surgency/extraversion and effortful control of temperament had posi-tive associations with their mastery motivation. Conclusion: Preschoolers with de-velopmental delay showed vulnerable in mastery motivation and their temperament have important associations with their mastery motivation. To detect children’s mastery motivation and temperament could be used to develop strategies to promote their engagement.