Despite numerous studies on the economic transnational connections of immigrants, focusing mainly on remittances to their home countries, the remittance behaviours and related factors of immigrants in South Korea, a country experiencing increased racial and ethnic diversity, remain relatively understudied. Applying a resource‐dependent and reactive transnationalism framework, this study examines the associations between assimilation, human capital, and immigrants' remittance behaviours. Additionally, we investigate whether perceived unfairness moderates these relationships, reflecting reactive transnationalism. Utilizing data from a 2021 Survey on Immigrants' Living Conditions and Labor Force (N = 7981), we delve into various remitting behaviours, including remittance frequency, the share of monthly remittances in expenditures, and the total remittance amount. The independent variables include assimilation indicators (length of stay in Korea and intention to remain), human capital factors (education and income) and perceived unfairness in the workplace. Ordinary least squares and logistic regression analyses were conducted to examine these relationships. Our findings support both linear and resource‐dependent transnationalism: assimilation and human capital levels are associated with immigrants' remittance behaviours. However, the interaction between perceived unfairness and reactive transnationalism was observed specifically for human capital, indicating that immigrants with higher human capital are more responsive to unfairness and discrimination. As a result, they may want to increase their self‐esteem by sending money back to their home country. This study not only contributes to understanding immigrant remittance behaviours in South Korea but also highlights the conceptual significance of examining remittance behaviours through reactive transnationalism, particularly the critical role of perceived unfairness among highly skilled immigrants.