This study aimed to determine the level of acceptability to Sinugbuanong Binisaya as the medium of instruction in selected elementary schools in General Santos North District, General Santos City Division School Year 2017-2018. The researcher employed descriptive phenomenology research to generate data on the level of acceptability relative to teachersâ€™ practices, beliefs, and management using Sinugbuanong Binisaya as the medium of instruction. The respondents were 66 Grades 1 to 3 General Santos North District teachers, General Santos City Division. A Focus Group Discussion was conducted to determine issues and concerns relative to acceptability of Sinugbuanong Binisaya as the medium of instruction. Findings of the study revealed that the demographic percentage of respondents according to the number of years in teaching rarely indicate that most of the teachers teaching the MTB-MLE were used with the K to 12 curriculums in which Sinugbuanong Binisaya was used as the medium of instruction since the said curriculum was implemented for 6 years now. The acceptance of the teachers in the implementation of the language policy revealed that 100 percent of the teachers as the primary implementers of the MTB-MLE are not attained because of the transition period from the bilingual education to the mother-tongue based education as part of the k to 12 curriculum reform of the Department of Education. Some problems encountered by the teachers in implementing mother tongue - based instruction include absence of books written in mother tongue, lack of vocabulary, and multicultural/ multilingual differences affect teaching in MTB. Moreover, learnersâ€™ performance in English was affected by the implementation of the new K to 12 curriculums.