This study aimed to describe the implementation of the social marketing strategy used by Gerakan Indonesia Diet Kantong Plastik, based on the problem of plastic waste in Indonesia. The purpose of this study was to find out how the "Diet Kantong Plastik" Social Marketing Strategy used by GIDKP in Indonesia in 2018. This research used qualitative research method using case study approach. This research was conducted in the GIDKP secretariat in South Jakarta. The data source in this study comes from the results of interviews with informants, literature studies, documentary and photographs. The validity of data is tested using source triangulation which means comparing and checking the validity of information obtained by source triangulation in qualitative research. The results of this study indicate that GIDKP has a strategic step, named three pillars that are used as a reference in each program and activity, there are advocacy, corporate engagement, and public education. Of the three pillars, the cooperation between GIDKP and the government has a big role in the successful marketing of “Diet Kantong Plastik”. Although GIDKP has three pillars that are used as references, GIDKP also used the steps of a social marketing strategy, although from the results of this study there are still some steps that have not been maximized by GIDKP.