This Case Study involves a study that adapted the convergent mixed-methods design to investigate target-language students' learning engagement in an academic writing class via translanguaging at the context of a university in Vietnam. A cohort of 116 English majors was conveniently sampled to respond to a closed-ended questionnaire, and 24 of them were invited to partake in the semistructured interviews. The data gained from the questionnaire were quantitatively processed by the SPSS software, whereas the data obtained from the semistructured interviews were qualitatively analyzed in terms of the content-analysis approach. In addition, this Case Study also discusses the research processes (e.g., research design, research instruments, sampling technique, and procedures for data collection and analysis) and practical challenges (e.g., lacking funding to conduct research and being outsiders). Therefore, by the end of this Case Study, readers will be able to understand the nature of the convergent mixed-methods design, analyze and critique the sampling technique, design research instruments, and establish the credibility and trustworthiness of the research findings so that they will be able to conduct a similar study. [This content is provided in the format of an e-book.]