Most experienced high school science teachers are asked at some point to serve as a mentor to a novice teacher. While mentor-training programs have been established in many states, they often only focus on how the mentor can help new science teachers understand and negotiate the school culture, such as how the school runs and where supplies are kept. Less attention is given to teaching mentors how to assist new science teachers to develop their content knowledge, general pedagogical knowledge, and science-specific pedagogical content knowledge. This article provides a checklist for mentor teachers to use when assessing the teaching skills and knowledge of new science teachers. This checklist helps prioritize what and how much assistance the new teacher needs. (Contains 2 figures.)