Multicultural teenagers in South Korea often suffer from psychological difficulties, such as social withdrawal and depression, due to communication difficulties, discrimination, and economic constraints. These emotional problems negatively affect career decision-making. However, little is known about the basic mechanism through which multicultural adolescents' internalizing problems affect their career decisions. This study expanded prior research by examining the sequential mediating effect of depression and achievement motivation in the relationship between social withdrawal and career decision-making and the moderated mediation effect of parental support in the causal pathway from social withdrawal to career decision-making via depression and achievement motivation. This study used panel data from the Multicultural Adolescents Panel Study (MAPS), a national survey. The results showed a sequential mediating effect of depression and achievement motivation, a moderating effect, and a moderating mediating effect of parental support. The results of this study imply that parental support is an essential factor that helps multicultural adolescents improve their career decision-making by alleviating depression and enhancing achievement motivation.