The growth of online learning has created a need for instructors who can competently teach online. This literature review explores the research questions, program recommendations, and future research suggestions related to professional development for online instructors. Articles were selected and coded based on date of publication and the context of the professional development. Results indicate that most research questions focused on (a) professional development programs, (b) instructors, and (c) instructors' online courses. Most program recommendations focused on (a) professional development programs, (b) context of professional development, and (c) instructors' activity during professional development. Future recommendations for research topics focused on professional development programs and instructors, while future recommendations for research methods focused on research design and institutional settings. The findings suggest that while professional development for online instructors is important, consistency in both design and delivery is lacking. Future research is needed to provide guidance to programs, instructors, and institutions leading to satisfaction and success for more online students.