Introduction: Streblus asper Lour. (Moraceae), known locally as Sheora or Khoi, has been traditionally used across South and Southeast Asian medicine systems including Ayurveda and folk practices in Assam, India for the treatment of intestinal worm infestations, filariasis, and gastrointestinal disorders. Despite this well-documented ethnopharmacological background, systematic in vitro evaluation of its anthelmintic potential using standardized bioassay models remains inadequate in the published literature. Aim of the study: To evaluate the in vitro anthelmintic activity of successive Soxhlet-derived chloroform, ethyl acetate, and hydroalcoholic (70% ethanol) leaf extracts of S. asper against Pheretima posthuma, using albendazole as a positive control, and to characterize the phytochemical profile of each extract. Materials and methods: Dried leaf powder (100 g) of S. asper, authenticated by voucher specimen (SA/BOT/2026/01), was subjected to successive Soxhlet extraction with chloroform, ethyl acetate, and 70% ethanol. Each extract was characterized by qualitative phytochemical screening. Anthelmintic activity was assessed using adult P. posthuma earthworms (n = 6 per group) at concentrations of 10, 20, and 40 mg/mL by recording time to paralysis (TP) and time to death (TD) at 37 ± 0.5°C. Data were analysed by one-way ANOVA with Tukey's post hoc test (p < 0.05). Results: Extract yields were 3.12% (chloroform), 4.56% (ethyl acetate), and 8.84% (ethanolic) w/w. The ethanolic extract tested strongly positive for tannins, saponins, flavonoids, alkaloids, and cardiac glycosides. All three extracts produced dose-dependent anthelmintic activity (p < 0.001 vs. negative control). At 40 mg/mL, the ethanolic extract produced paralysis in 23.40 ± 0.82 min and death in 39.60 ± 0.98 min, compared to albendazole at 16.00 ± 0.58 min and 27.80 ± 0.74 min, respectively. Potency ranking at all doses: albendazole > ethanolic > ethyl acetate > chloroform extract. Conclusions: The hydroalcoholic leaf extract of S. asper exhibits significant anthelmintic activity attributable to the synergistic action of tannins, saponins, flavonoids, and cardiac glycosides. These findings provide rigorous pharmacological substantiation for the ethnomedicinal use of this plant as an anthelmintic and identify it as a promising candidate for further bioactivity-guided fractionation and in vivo validation.