Peer assessment (PA) is generally effective, and especially important for school teachers, as the experience might lead teachers to use PA more skilfully with school students. Digital PA (using computers) becomes more important as universities switch to online learning. This systematic review of research literature on digital PA for pre-service and in-service teachers encompasses: online/web-based, video, Massive Open Online Courses, digital frameworks to organize/structure PA, e-portfolios, Personal Digital Assistants (PDAs), Facebook, iPads and wikis. It contained 43 papers and all but one reported mainly positive effects. Potential moderator variables were considered, but studies rarely reported many of them. Few studies had control groups, only two reported Effect Sizes, and none reported implementation fidelity or follow-up. There was little evidence for carry-over of PA practices into later teaching of school children. However, the potential moderator variables provide a template for future reviews of PA and the design of PA by teachers.