This study aims at delving into the effect of applying TbI (Technology based Instruction) lesson plan to pre-service teachers’ (PSTs) Technological Pedagogical Content Knowledge (TPACK) self-efficacy in a microteaching course. TbI lesson plan was developed following Niess’s technology integration framework. The experimental research with pre-post measurements design was conducted in an English Department in a public university in West Nusa Tenggara, Indonesia. The data-gathering process was done by administering the TPACK self-efficacy questionnaire and conducting a semi-structured interview. The participants were 23 PSTs who joined a microteaching course where the researcher became the teacher. The quantitative data were analyzed statistically through SPSS 24 version and supported by the PSTs responses which were thematically analyzed. The results showed that the treatment affected positively to PSTs' self-efficacy which was later recommended to inhibit technological knowledge prior to other TPACK divisions to PSTs. This favorable effect was confirmed by six participants' post-interview comments, in which they claimed all of the benefits of using a TbI lesson plan to improve their microteaching performance and confidence to use technology for EFL teaching. Henceforth, this study implies the urgency to apply similar instruction to mediate challenges of technology integration in EFL teaching.