Estimates of “Street Youth” (SY) (those who live/work on the streets) show 150 million around the world, with approximately 50,000 in Kenya alone as of 2018. Challenges these youth face remain a significant barrier to national governments achieving Sustainable Development Goal 4 (Quality Education) targets, as formal schools limit access or fail to provide meaningful and supported learning experiences for SY. However, informal learning spaces that empower youth to solve problems themselves may provide them with the knowledge and skills they are denied by formal schools. SY rescue, rehabilitation, and reintegration centers all around the world emphasize and place education at the center of their operations. Recommendations for educational services for SY include providing flexible, alternative education and skills training for youth unable or unwilling to return to school. However, the lack of skilled professionals working with the SY population is one of the most critical challenges.<div>To meet the learning needs of vast numbers of SY, teachers already connected to this population must be trained in teaching more empowering, skill-based courses such as engineering, which are typically complex. Such innovative, problem-centered curricula demand skilled teachers who are prepared to facilitate a more student-centered classroom. However, sub-Saharan Africa faces a shortage of 17 million formally qualified teachers, even for its formal public schools. Therefore, connecting with the teachers in the context and training them in engineering teaching is crucial. Researchers have long argued the need for teacher professional development to be continuous and long-term. Through this dissertation, I present a Design-Based Research (DBR) study of untrained Teacher Professional Development (TPD) in collaboration with three aspiring engineering teachers at an alternative school for SY in western Kenya. I draw on the theoretical framework of Situated Learning and Communities of Practice (CoP) to discuss the outcomes of a three-phase professional development program. Each phase was designed using the recommendation from McKenney et al. (2006) to include three iterative micro-cycles of analysis, design, and evaluation leading to a meso-cycle. In total, three meso-cycles were completed to arrive at DBR’s final phase of reflection and generation of design principles.<br></div><div>In the first phase, teachers in this study adopted reflective practice strategies to increase their awareness of the practice. Analysis from the study showed that the teachers individually and collectively showed resilience to challenging and complex experiences by establishing a strong foundation for the community of practice. In the second phase, teachers engaged in action research to improve both teaching and learning outcomes. Results demonstrated increased active participation of the teachers in their teaching practice, and developed new understandings of engineering teaching. However, the first two studies also showed the challenges limiting the teachers from constructing an engineering teacher identity and unresolved questions about the sustainability of the TPD. Therefore, in the last phase, the teachers adopted mentoring new teachers as a strategy to develop their identities and sustain the engineering TPD.<br></div><div>The findings from the three phases resulted in generation of design outcomes that include a situated understanding of the theory in this fragile context and design principles that are transferable in comparable settings. Implications of this work suggest a sustainable teacher professional development model for untrained engineering teachers in fragile contexts and present relevant design principles for the CoP.<br></div>