Associated health effects from algal toxin exposure are a growing concern for human and animal health. Algal toxin poisonings may occur from contact with or consumption of water supplies or from ingestion of contaminated animals. The U.S. Federal Government owns or holds in trust about 259 million hectares of land, in addition to the Trust species obligations. We completed the first comprehensive review of potential toxin-producing algal blooms in surface waters on Federal lands and Trust species exposed to algal toxins. Events were sorted into three tiers based on potentially toxic algae abundance or toxin concentration and related effects on animal morbidity and mortality. At least 11.1% of Federal lands are known to have been affected by algal events, but exposure is likely underreported. The occurrence of potential toxin producers and their toxins (Tier 1) have been documented 337 times, health advisory threshold exceedances (Tier 2) were reported 943 times, and 86 events involved animal sickness or death linked to cyanobacteria or marine toxins (Tier 3). Trust species exposed to cyano- or algal toxins included marine mammals, migratory birds, threatened and endangered species, and species of concern. We report numerous data gaps ranging from potential effects on human health from consuming intoxicated animals to the infrequency of measuring and reporting certain toxins. Improvements to field and laboratory methods, more consistent evaluation of toxin exposure, decreased latency on data analysis, delivery and interpretation will be necessary to improve response and management strategies for protecting human and animal health where issues persist.