This paper explores challenges of teaching in relation to teachers' efficacy for 49 teachers who were part of a year-long teacher development program (PD) called the UrbanSTEM program. This program took place in an urban school district that serves over 300,000 students. This research asked if there are common challenges that urban teachers face when teaching STEM content. If so, do these challenges influence efficacy of teachers, and did the teachers' efficacy change over time due to their involvement in the UrbanSTEM program? Teachers identified external challenges, lack of resources, and organizational contexts having effect on their capacity to address the needs of their diverse students. Although the study did not identify significant relationship between challenges and efficacy, the study did show that this PD was successful in supporting urban STEM teachers by significantly increasing their self-efficacy