Objective To investigate the inhibitory effect of Poecilobdella manillensis ( PM) extract on kappa-carrageenan (KCG)-induced tail thrombosis in mice. Methods KM mice were treated with intraperitoneal PM extract JC-17 (2. 5, 25, or 100 mg / kg) or heparin sodium (50 mg / kg) for 7 consecutive days. Tail thrombosis was induced 1 hour after the last dose by injection of 0. 5% KCG. Results The tail-blackening rate in the model group (mice were treated with 0. 2 mL of 0. 5% KCG) at 48 h was ( 94. 91 ± 3. 93)%, confirming successful induction of thrombosis. Mice in the PM-treated groups ( L, M, H) exhibited dose-dependent reductions in tail blackening. The extract significantly prolonged the prothrombin time ( PT) and reduced fibrinogen ( FIB) levels.Splenic levels of tumor necrosis factor (TNF)-α, interleukin-1β(IL-1β), and interleukin-6(IL-6) were elevated in the model group. All PM-treated groups and PC group showed significant suppression of these inflammatory cytokines. Conclusions PM extract JC-17 effectively inhibits KCG-induced tail thrombosis and exhibits anti-inflammatory activity, suggesting its potential therapeutic value for inflammation-associated thrombotic disorders.