Hexabromocyclododecanes (HBCDs) are nonaromatic, brominated cyclic alkanes used primarily as additive flame retardants in polystyrene and textile products for fire-protection. HBCDs are now ubiquitous organic contaminants, such as in air, sediment, animal tissue, even in human blood and milk. Technical HBCDs are composed of three diastereoisomers. Structural dissimilarities of α-, β-, and γ-HBCD raise substantial differences in physical and chemical properties (polarity, dipole moment and solubility in water), which results in their distinctive environmental behavior and toxicological risks. By zebrafish (Danio rerio)e exposed to individual HBCD diastereoisomers (α-, β-, and γ-HBCD), the results were found. The depuration of α-, β- and γ-HBCD in zebrafish all followed the first-order process. Bioaccumulation parameters of three diastereoisomers are different between low and high dose, suggesting the bioaccumulation of them is concentration dependent. Calculated assimilation efficiency (AE), biomagnification factor (BMF) and half-lives (t1/2) of α-HBCD are the highest among three diastereoisomers. Furthermore, the study shows that zebrafish could biotransform g-HBCD to α-HBCD. The highest AE, BMF and t1/2 of α-HBCD and bioisomerization of γ-HBCD to α-HBCD could explain why α-HBCD appears to be dominant in biota samples. EFs for α- and γ-HBCD in zebrfish estimated at different times of bioaccumulation and depuration are all significantly greater than those in corresponding food (P < 0.05), indicating selective enrichments of (+) α-enantiomer and (+) γ-enantiomer relative to (-) α-enantiomer and (-) γ-enantiomer, respectively.