Sekolah Siaga Kependudukan is a population education program that targets the younger generation through the integration of population materials into subjects in schools with output in the form of understanding population and minimizing child marriage. The socialization of the SSK program by the BKKBN DIY was conducted to give teachers an understanding of the importance of population issues delivered to students and offer programs to schools. The purpose of this research is to describe how the communication strategy of social marketing by BKKBN DIY in socializing Sekolah Siaga Kependudukan Program in Yogyakarta in 2016-2018. The type of research used is descriptive qualitative. The technique of data collection was done by interviewing the BKKBN DIY and the school that implemented the SSK program and documentation obtained from the BKKBN DIY. The results of the study show that the communication strategy of social marketing carried out by the BKKBN DIY in sosializing the SSK program prioritizes direct or face-to-face communication. BKKBN DIY also uses media websites in addition to print media in the form of information books about the SSK program, namely through the website CIS DALDUK and BKKBN DIY. In socializing the SSK program, BKKBN DIY has succeeded in giving understanding to teachers the importance of population education to students and how it is implemented in schools, so that schools are willing to participate in implementing the SSK program.