Reforms in STEM education call for reframing teachers' pedagogical content knowledge (PCK) by focusing on development of students' knowledge and scientific literacy through socioscientific issues (Lee, 2016; Zeidler, 2016; Johnson et al., 2022). We developed a two-year professional development (PD) for 6-12th grade STEM teachers that embedded SSI framework into their teaching. An analysis of survey and interview data from 24 teachers over two years and data from nine focus group interviews and pre/post surveys were used to answer our research questions on the enhancement of teachers' SSI pedagogical practices, and PCK for integrating social justice to their lessons. Our findings suggest that the PD was beneficial to participating teachers and improved their comfortability and experience teaching SSI. Moreover, our teachers developed PCK for teaching STEM through the lens of social justice in several ways, including considering different perspectives and backgrounds, connecting to current events and issues relevant to students' lives and engaging students in decision making and problem solving to make a positive impact in their communities.