Background: Flame retardant (FR) substances are known to pose a risk to environmental health. A list of potential FR substances has been developed; however, detailed information on the risk, or hazard of such substances to the environment, specifically ecologically relevant endpoints involving animals, plants, bacteria and fungi, has not yet been collated. Methods: The main objective of this study is to identify, organise and group existing primary evidence of the ecologically relevant (eco)toxicological effects of FR substances to the environment. Search Strategy: We will search several databases across two electronic academic indexes (Scopus and Web of Science [All Collections]). Eligibility criteria: Eligible studies must contain primary research investigating the risk (or hazard) of one or more included FR substances and study an ecologically relevant effect in any non-human animal, plant, bacteria and/or fungi. Ecologically relevant effects include impacts on growth, development, survival, reproduction and behaviour. Screening & extraction: Articles will be screened at title and abstract, before a full-text review. All articles will be screened by a single reviewer, with a second reviewer assessing articles for consistency. Data extraction will be performed on all articles included at full text, with articles that do not meet the eligibility criteria excluded. All articles excluded at full text will be confirmed by a second reviewer. Study mapping & reporting: Results will be published in a narrative summary and visualised in a publicly available, user-friendly, interactive and interrogable evidence map.