The purpose of our study was to examine mathematics and science pre-service teachers' perceptions of their mentoring experiences during their 1st year in the Teaching Residency Program for Critical Shortage Areas, an initiative designed to recruit, prepare, and retain teachers for high-need urban schools. Results from this mixed-methods study illustrated pedagogical aspects and mentor characteristics that enhanced and impeded pre-service teachers' growth and development. Therefore, professional development, especially working with adults, must also include frequent monitoring of the mentoring relationships to identify problematic situations. Our findings also suggested that an extended field experience helps deter deficit thinking about a diverse student population. The dynamics of teaching alongside a mentor through a residency program, coupled with the challenges of an urban setting, provide an opportunity for researchers to continue to examine pre-service teachers' development and to identify effective practices to build mentor capacity.