Sphagneticola trilobata (L.) Pruski is considered as one of the world’s worst alien invasive species. The extent of mortality of earthworm Perionyx excavatus Perrier exposed to 2.5 × 102, 5.0 × 102 and 7.5 × 102 g/L of aqueous extracts of fresh and dry S. trilobata plants was studied. The experiment was carried out in plastic containers containing 3:1 mixture of compost and topsoil. The mortality of all the P. excavates, exposed to fresh plant extracts of 5.0 × 102, 7.5 × 102 g/L and dry plant extract of 7.5 × 102 g/L, occurred within four weeks. The percentage mortality of earthworms due to S. trilobata extracts was significantly higher than in the control (one-way ANOVA, p=0.05). Coiling, abnormal swelling, mucous secretion, blooding, and fragmentation were noticed in earthworms that were dead due to S. trilobata plant extracts. The percentage mortality of earthworms showed a strong positive, linear relationship (r2=0.98; p=0.05) with the different concentrations of aqueous extracts of S. trilobata. S. trilobata should not be used in agricultural activities such as use of it as live mulch to improve soil conditions or producing compost fertilizer as the aqueous extracts of S. trilobata were highly toxic to P. excavatus.