The purpose of this phenomenological inquiry was to investigate the gains and drawbacks on mother tongue-based instruction from the perspective of the non-Maranao teachers and to understand the lived experiences of the non-Maranao teachers who did not speak the students’ mother-tongue. This study utilized the purposive sampling technique which included the ten non-Maranao teachers who served as informants. These informants utilized Mother Tongue Based Instruction in multilingual classes. In-depth interview and focus group discussion were employed in the data collection. Employing thematic analysis, the researcher found various themes. The non-Maranao teachers’ perception of the gains on the use of Mother Tongue Based-Instruction included teachers’ fluency in mother tongue, students’ readiness to learn through mother tongue, teachers’ gain of skills in improvising instructional materials written in mother tongue, teachers’ adeptness in the adaptation of teaching strategy, and students’ acculturation to Cebuano language. The drawbacks on the use of Mother Tongue Based-Instruction were insufficient instructional resources, confusing polysemous words in SinugbuanongBinisaya terms, teachers’ difficulty in the translation to and from educational institutional materials, and incongruence of the medium of institutional and the District test materials. Finally, the insights shared by the participants included the need to conduct remedial classes, crafting of glossary of SinugbuanongBisaya, encourage the use of home language (L1) in mother tongue instruction, and boost affective domain of the students in using mother tongue.