Korean missionaries and Korean diaspora churches are all around the world now. In fact, Korea is widely known as the second-largest missionary sending country in the world, and the country where the biggest church in the world is located. However, although Korean diaspora churches are located in strategic places for world mission, many are reaching out to only Koreans. Of course, they are engaging in various forms of mission. But mission is not their main pursuit. They tend to focus more on internal programs, and differentiate those programs from mission. Missional churches, on the other hand, have a different understanding. They think of the church as having one vocation: participation in the missio Dei—that is, the Triune God’s own mission. In other words, traditional churches have programs, some of which focus on mission; in contrast, missional churches focus mainly on mission and seek to bring all their programs to bear on that task. This study, in which the author commends the latter ecclesiological stance, explores how Korean diaspora churches in North America might be able to move from a traditional stance to a missional one. Utilizing three transformation theories as a framework for analysis, and working from data from interviews with leaders from ten Korean churches in North America and North American-based Korean missional leaders, plus library research and the records and histories of the churches studied, this study concluded that the authoritarian model of pastoral leadership in first generation Korean diaspora churches in North America militates against the employment of any change process that does not focus first and foremost on senior pastors. Given the support of the senior pastor, the study further recommends a strategy for change that is tailored to the culture of first generation North America Korean churches.