Organotin carboxylates of the general formulae R2SnL2 and R3SnL, where R = CH3, n-C4H9, C6H5, CH2C6H5 and L = 1-ethyl-1,4-dihydro-7-methyl-4-oxo-1,8-naphthyridine-3-carboxylic acid (nalidixic acid), have been prepared. These compounds were characterized by FT-IR, mass and multinuclear NMR (H-1, C-13 and Sn-119) spectroscopy. The geometry around the tin atom is compared both in solution and in solid state. These compounds were also screened for their antifungal and antibacterial activities.