The increasing concern over the environmental presence of β-N-Methylamino-L-alanine (BMAA), a toxin primarily produced by cyanobacteria and diatoms, has stimulated numerous studies to evaluate the risk for exposed populations, mainly aquatic organisms and humans. This study focuses on the toxicity of environmental concentrations of BMAA and its isomers, l-2,4 diaminobutyric acid dihydrochloride (DAB) and N-(2-aminoethyl) glycine (AEG) on zebrafish embryo development (ng.L -1 ). Presence of BMAA in various environments, including aquatic sources, air, and desert crusts, has raised concerns due to its potential link to neurodegenerative diseases such as the amyotrophic lateral sclerosis/parkinsonism dementia complex (ALS/PDC). Despite its known toxicity at high concentrations, there is limited information on the effects of environmental concentrations of BMAA and its isomers. These isomers are often found in association with BMAA and have been detected in seafood intended for human consumption, indicating potential risks from bioaccumulation and biomagnification. Zebrafish embryos have been chosen as a model due to their relevance for embryonic development and toxicity studies. The study employed fish embryo acute toxicity tests and behavioural analyses to specifically assess the sublethal effects of BMAA, DAB, and AEG. The results demonstrated larval mortality rates between 0 % and 3.75 %, while morphological defects were detected across all tested concentrations for each molecule. Behavioural analyses showed alterations in swimming behaviour. Unexpectedly, the changes in morphology and locomotion of the zebrafish larvae were detected more frequently at the lowest concentrations tested, suggesting potential nonmonotonic dose responses. Overall, this research underscores the environmental risks associated with BMAA and its isomers, highlighting the importance of continuous monitoring and understanding of their sublethal effects on aquatic organisms and potential implications for human health. Further studies are warranted to elucidate the mechanisms of toxicity, evaluate long-term effects, and assess the risks associated with chronic exposure to these toxins.