<p>Executive functions (EF) emerge early in childhood and are crucial for development into adulthood. Few studies have explored the relationship between mastery motivation (MM) and EF in the context of neurodevelopmental status across cultures. This study examined: (1) the differences in EF of young children in Taiwanese and U.S. cultures; (2) the relationships between MM and EF; and (3) the relationships of these constructs regarding child neurodevelopmental status in typically developing (TD) and developmentally delayed (DD) children across cultures. This cross-cultural comparative study was conducted with children from Taiwan (DD: <i>N</i> = 26, TD: <i>N</i> = 26) and the United States (DD: <i>N</i> = 20, TD: <i>N</i> = 33). EF was measured using the BRIEF-P; MM, with the revised Dimensions of Mastery Questionnaire (DMQ 18); and neurodevelopmental ability, with the Bayley Scales of Infant Toddler Development (BSID III) (US) or the Comprehensive Developmental Inventory for Infants and Toddlers (Taiwan). Analyses included t-tests and correlations. For TD children, EF scores were similar between countries, except for Working Memory. For DD children, Taiwanese parents reported more EF deficits on all scales except Shift. MM was positively associated with better inhibitory control and working memory in both countries. In the United States, TD children with higher cognitive and language scores demonstrated better EF than DD peers. Findings highlight both cultural differences and similarities in EF, MM, and neurodevelopmental status. Early intervention worldwide should focus on enhancing EF to prevent or buffer later school failure, with professionals supporting parents to foster EF using authentic, developmentally appropriate opportunities. </p>