Objectives: This study examined the moderated mediating effect of bicultural acceptance attitudes by Korean ability on the relationship between self-esteem and the national identity of children in multicultural families. Methods: This study used data from the second wave of the Multicultural Adolescents Panel Study (MAPS) of fourth grade elementary school students. A total of 442 participants (226 (53.56%) boys, Mage = 10.22, SD = .514) answered self-report questionnaires on self-esteem, Korean ability, bicultural attitudes, and national identity. PROCESS Macro model 8 was used to analyze the moderated mediation effect between variables. Results: The conditional direct effect of the interaction between self-esteem and Korean ability on national identity was significant. Furthermore, the conditional indirect effect of this interaction on national identity through the mediation of bicultural acceptance attitudes were significant, and the relative influence of this conditional indirect effect was strongest in the group with low Korean ability. Conclusions: This study lays the groundwork for understanding how children from multicultural families develop national identity. It highlights the importance of considering factors such as self-esteem, Korean language proficiency, and bicultural acceptance to enhance the effectiveness of supportive programs.