Literature has documented the benefits of problem-based learning (PBL), but also shown significant barriers to using PBL in K-12 education. Yet, the research describing why and how K-12 teachers implement PBL is insufficient. In this qualitative study, using semi-structured interviews, we investigate why 25 middle school teachers chose to implement a technology-enriched PBL program, challenges they encountered, and facilitation strategies they used to address those challenges. The findings of this study showed that teachers were motivated not only by PBL's alignment with their beliefs, but by their students' positive learning outcomes. The interviews revealed two significant pedagogical challenges for teachers: (a) knowing when to let go of control as opposed to when to step in to facilitate, and (b) determining how to provide additional support to students with special needs. Nine types of facilitation strategies to deal with these challenges were identified.