This study investigated how pre-service English teachers develop and use MICT (mobile information and communication technology)-TPACK (technological pedagogy and content knowledge) to select and use mobile applications for their micro teaching in a pre-service teacher training program. Although mobile technology has rapidly developed with the adoption of mobile multimedia devices and applications, the use of pre-service teachers’ TPACK is still limited to lower-level searches and to a mere tool for content presentations. The participants were nine students in a pre-service teacher training course in a four-year women’s university. Several research methods such as surveys, participant observations, micro teaching and interviews were utilized. The results of the study show the concept of TPACK needs to be extended to MICT-TPACK in this mobile age. The use of pre-service English teachers’ MICT-TPACK impacted and changed their concept of pedagogy to heutagogy. The teachers used mobile applications to facilitate their students’ inquiry-based learning of English as a subject as well as a medium of digital literacy. In order to select mobile applications for their lesson, the teachers developed a modified version of quality criteria for mobile applications. This study suggests there should be well-developed quality criteria for evaluating affordances of mobile applications.