Objectives: Plant-based medicines have had a long-standing history of use in psychiatric disorders. Highly quantified and standardized extracts or isolates may be termed “phytoceuticals,” in a similar way that medicinal nutrients are termed as “nutraceuticals.” Over the past 2 decades, several meta-analyses have examined the data for a range of plant-based medicines in the treatment of psychiatric disorders. The aim of this international project is to provide a “meta-review” of this top-tier evidence. Methods: We identified, synthesized, and appraised all available up to date meta-analyses... of randomized controlled trials (RCTs) reporting on the efficacy and effectiveness of individual phytoceuticals across all major psychiatric disorders. Results: Our systematic search identified 9 relevant meta-analyses of RCTs, with primary analyses including outcome data from 5,927 individuals. Supportive meta-analytic evidence was found for St John’s wort for major depressive disorder (MDD); curcumin and saffron for MDD or depression symptoms, and ginkgo for total and negative symptoms in schizophrenia. Kava was not effective in treating diagnosed anxiety disorders. We also provide details on 22 traditional Chinese herbal medicine formulas’ meta-analyses (primarily for depression studies), all of which revealed highly significant and large effect sizes. Their methodology, reporting, and potential publication bias were, however, of marked concern. The same caveat was noted for the curcumin, ginkgo, and saffron meta-analyses, which may also have significant publication bias. Conclusions: More rigorous international studies are required to validate the efficacy of these phytoceuticals before treatment recommendations can be made. In conclusion, the breadth of data tentatively supports several phytoceuticals which may be effective for mental disorders alongside pharmaceutical, psychological therapies, and standard lifestyle recommendations.