Socioscientific issues (SSI) have been found to improve scientific literacy skills among K-12 students. Existing literature shows, however, that elementary preservice teachers are reluctant to implement SSI due to a lack of confidence with subject matter knowledge and knowledge of instruction concerning SSI. Previous research has focused on helping elementary preservice teachers overcome these concerns through microteaching, adapting existing curricula, and experiencing SSI through methods courses. While it has been noted that formal preparation is required for preservice teachers to feel confident in their abilities to facilitate SSI, little has been done to prepare elementary preservice teachers to facilitate SSI during field experiences. In this study, we explored the factors that influenced elementary preservice teachers' instructional decision-making while planning and enacting SSI-based instruction in the classroom. Community of practice (CoP) meetings provided formal training to prepare these elementary preservice teachers to facilitate SSI. Recordings of the CoP meetings, reflective journals, observations, and interviews served as data sources. Our findings revealed knowledge of students, instructional knowledge, and context as most influential in these elementary preservice teachers' pedagogical reasoning concerning SSI-based instruction, while subject matter knowledge was the least considered. We discuss these findings and offer recommendations for how to use these considerations when planning future research to study elementary preservice teachers' SSI-based instructional practice.