<p> This study investigated the sorption and desorption behaviors of polycyclic aromatic hydrocarbons (PAHs) on marine biodegradable plastics (MBPs) before and after seawater biodegradation. The sorption of three PAHs (phenanthrene, fluoranthene, and pyrene) onto the MBPs and their subsequent desorption under simulated intestinal conditions were evaluated. The MBPs used were poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH, 3HH = 6&#xa0;mol%) and poly(ε-caprolactone) (PCL); to mimic marine debris, pellets of these MBPs were pre-degraded in seawater, and sorption behaviors on virgin MBPs and low-density polyethylene (LDPE) were investigated. The linear sorption coefficients (log K_Dis) ranged from 2.805 to 3.251, 4.525–5.217, and 4.047–4.473 for PHBH, PCL, and LDPE, respectively. Importantly, the differences in sorption coefficients between virgin and seawater-biodegraded pellets (Δlog K_Dis = 0.019–0.079 for PHBH and 0.026–0.239 for PCL) were small and insignificant compared to the variations among the tested plastics (1.640 &lt; Δlog K_Dis &lt; 2.039), indicating that PAH sorption coefficients on MBPs remained almost unchanged after seawater biodegradation, and that polymer identity exerted a stronger control on PAH sorption than the biodegradation process under the tested conditions. Calculated PAH concentrations in simulated intestinal fluids were 0.9–2.3-times higher than those in seawater for PHBH, 2.8–11.9-times higher for PCL, and 5.4–12.4-times higher for LDPE. These results show that both biodegradable and non-biodegradable plastics substantially enriched PAHs in intestinal fluids, whereas seawater biodegradation of MBPs alone did not enhance their PAH sorption. The study provides quantitative constraints on the role of MBPs in contaminant exposure to marine organisms.</p> Graphical Abstract <p></p>