In-work poverty (IWP) has emerged as a critical issue in the East Asian welfare states (Japan, Korea and Taiwan) during the past two decades. However, a comparative lens to empirically study IWP in East Asian economies is absent due to the lack of a comparable database. The authors argue that three East Asian welfare states have different patterns of IWP due to different patterns of capitalist structure and labour market. This chapter uses the Luxembourg Income Study (LIS) to show different patterns of IWP in East Asia. Japan and Korea adopted a series of social policies, including activation and family policies, under the umbrella of social investment, although in the contexts of different political discourses and trajectories. By contrast, only a few temporary policy measures were introduced to help the working poor in Taiwan.