This qualitative study investigated in-service teachers' perceptions of a cohort- mentoring program leading to certification in English as a Second Language (ESL). Interview data from 19 members of a single cohort at a large, urban university showed that participants valued both the support and augmented skills-development that they felt the mentoring component contributed and the supportive, collaborative environment provided by the cohort model. Many also reported that the ESL-targeted strategies were helpful in teaching to all student populations and that program participation contributed to their taking on leadership roles, particularly in professional development, in their schools and districts. The results can contribute to efforts to refine instructional models in meeting the need for more trained ESL teachers in U.S. schools.