The phenomenon of 'runaway' migrant contract workers in Taiwan has attracted the attention of both the Taiwanese and Vietnamese governments. According to the National Immigration Agency in Taiwan, by 31 October 2017, the total number of runaway foreign workers was 52,891. Of these, Vietnamese workers were the largest subgroup, at 25,626 people. This research draws on data from indepth interviews with 49 'runaway' Vietnamese migrant workers in Taiwan. This research study not only explores the factors that force some Vietnamese migrant workers to give up their legal status and become outlaws in Taiwan, but it also provides a detailed understanding of th e daily lives and working conditions of illegal Vietnamese workers. This research study reveals that migrant social networks play an important role in the lives of Vietnamese workers, offering a vital source of material and psychological support. Moreover, the research also shows how huge debt and guest-worker policies force Vietnamese migrant workers to run away.