Psychology training clinics provide evidence-based, cost-effective psychological services to the general public, while at the same time providing a training ground for future psychotherapists. Research in training clinics can advance the clinical literature, train psychotherapists in evidence-based practice and improve outcomes for clients. However, since the last published review of research published in psychology training clinics (Todd, Kurcias, & Gloster, 1994), it is unclear how much the training clinic literature has advanced in the last two decades or if findings can be synthesized across sites. A systematic, quantitative literature review with strict inclusion and exclusion criteria described 257 empirical studies conducted in training clinics since the previous review (1993-2015). Studies were coded and categorized into themes by three independent raters. Studies explored the nature and organization of training clinics, client characteristics, assessment, intervention, staff and clinical training, as well as research and research training. Across themes, it appeared that the literature has broadened extensively, highlighting that researchers have embraced training clinics as a sample source. While there was a great breadth of topics researched, there remains insufficient depth in the majority of areas, and a need for multi-site collaborations with a shared research agenda across training clinics. The review highlighted the extent to which training clinics are valuable research locations, although more research is needed to compare different training clinics and between training clinics versus non-training clinics.