Abstract The climbing perch Anabas testudineus is widespread in the inland waters of Vietnam and according to its ecology could have contact with a floating plastic waste. The fragments of expanded polystyrene (EPS) detected into the fresh waters of Vietnam in Khanh Hoa, Lam Dong, Phu Yen provinces. Our study was focused on estimation of probability of ingestion of EPS pellets (size 2.5–3.5 mm) by adult climbing perch. In the experiments three types of treatment pellets were proposed to fish: 24 feed pellets (Fp), 24 expanded polystyrene pellets (Pp), 12 feed & 12 expanded polystyrene pellets (FPp). Fish grasping time of first pellet was independent in all treatment types. The time grasping of 12 th pellet was insignificant in Fp (63 s) and Pp (75 s). Climbing perch was grasping and ingesting of 24 th Fp significantly (p = 0.02) earlier (143 s), than grasping of 24 th Pp (817 s). Fish with FPp treatment was grasping feed along with EPS pellets, but grasping of 12 th Fp was significantly (p = 0.02) earlier (49 s), then 12 th Pp (193 s). By the end of tests fish ingested all feed pellets. We discovered that climbing perch grasped Pp and kept them in oral cavity, but always rejected them in 100% cases. This result evidenced that climbing perch has effective defense mechanism avoiding ingestion of expanded polystyrene pellets with size 2.5–3.5 mm, which realized by taste system and tactile reception of fish.