Young adult North Korean defectors (hereafter, North Korean millennials [NKMs]) are a growing and distinctive group. Even though they constitute the majority of defectors and show different characteristics from previous generations, relatively little attention has been paid to NKMs in both academic and practical areas. Specifically, little is known about how NKMs develop their career paths in South Korea. This study examines the process of NKMs’ career development activities, focusing on their challenges, structural tensions (contradictions) within the activities, and their learning from the process of resolving difficulties under the lens of cultural–historical activity theory (CHAT). This ethnographic study not only broadens understandings about NKMs but also elucidates their career development situation in South Korea. The findings of this study provide meaningful and practical suggestions to create a road map of career development for NKMs and implications for career development of migrants, refugees, and internally displaced persons.