This mixed-methods investigation examined the collaborative mentoring of teachers in a large school system in the south-eastern United States. The investigation was guided by two purposes. The first was to examine collaborative mentoring as unstructured peer-to-peer coaching. The second was to examine how licensure courses contributed to the emergence of collaborative mentoring. After completing courses, 84 teachers reported significant increases in frequency and duration of interactions for sharing best practices with colleagues. Of 33 novice teachers recently trained in teaching ELLs, most found themselves mentoring veteran teachers yet untrained in teaching this student group.