This study used a teacher efficacy framework to describe the perceptions of high and low implementers of content literacy instruction in the context of a year-long professional development program. Interviews from middle and high school content teachers illustrated efficacy differences between teachers who demonstrated high and low levels of content literacy implementation. High implementers exhibited higher levels of general, personal, and collective efficacy, whereas low implementers exhibited lower levels of efficacy for literacy teaching. Although both high and low implementers perceived content literacy positively, high implementers were characterized by persistence in overcoming barriers associated with content literacy implementation. (Contains 1 table.)