Isatin (1H-indole-2,3-dione) and its derivatives belong to an important class of indole-fused heterocyclic compounds. Isatin serves as a versatile intermediate for the synthesis of a wide range of biologically active heterocycles. The present work provides a detailed account of the synthesis of isatin-based Schiff bases and their corresponding thiazolidine-4-one derivatives, which can be further utilized for the development of novel heterocyclic molecules.The isatin moiety exhibits a broad spectrum of biological and pharmacological activities, including antihypertensive, analgesic, anthelmintic, antitumor, antiviral, antifungal, anticonvulsant, anti-Parkinson, anti-HIV, anti tubercular, and antioxidant activities.In the present study, a series of isatin and Schiff base derivatives were synthesized. Initially, isatin was reacted with acetaldehyde in the presence of sodium hydroxide and ethanol to yield an aldol-condensed product at the C-2 position. This intermediate was further reacted with nitro-substituted benzene diamines in ethanol under basic conditions to form Schiff base derivatives. The synthesized Schiff bases were subsequently cyclized with thioglycolic acid to obtain thiazolidine-4-one derivatives.The progress and completion of the reactions were monitored by thin-layer chromatography (TLC). The synthesized compounds were evaluated for anthelmintic activity using earthworms as the experimental model. Structural characterization of the compounds was carried out using ¹H-NMR spectroscopy and mass spectrometry, which confirmed the proposed structures.