A new series of bis-[4-methoxy-3-[3-(4-fluorophenyl)-6-(4-methylphenyl)-2-(aryl)-3,3a,5,6-tetrahydro-2H-pyrazolo[3,4-d][1,3]thiazol-5-yl]phenyl]methanes 6a—r was synthesized by the reaction of arylidine derivative of methylene-bis-thiazolidinones 5a—c with aryl/alkyl hydrazines. Chemical structures of all the new compounds were established by IR, ¹H-NMR, ¹³C-NMR, MS and elemental data. The compounds 6a—r were evaluated for their nematicidal activity against Ditylenchus myceliophagus and Caenorhabdites elegans by aqueous in vitro screening technique. Amongst them compounds containing N-benzylpyrazole moiety (6d, 6j, 6p), and N-methylpyrazole moiety (6f, 6l, 6r) showed significant nematicidal activity against both the test nematodes with LD₅₀ 160—210 ppm, almost equal to the oxamyl standard. Further, these compounds 6a—r were screened for their antibacterial (MZI, MIC and MBC) activity against three representative Gram-positive bacteria viz. Bacillus subtilis (MTCC 441), Bacillus sphaericus (MTCC 11), Staphylococcus aureus (MTCC 96) and three Gram-negative bacteria viz. Pseudomonas aeruginosa (MTCC 741), Klebsiella aerogenes (MTCC 39), Chromobacterium violaceum (MTCC 2656) and also screened for their antifungal (MZI, MIC and MFC) activity against four fungal organisms viz. Candida albicans (ATCC 10231), Aspergillus fumigatus (HIC 6094), Trichophyton rubrum (IFO 9185) and Trichophyton mentagrophytes (IFO 40996). Most of these new compounds showed appreciable activity against test bacteria and fungi, and emerged as potential molecules for further development.