Radical-initiated terpolymerization of maleic anhydride (MA), N-vinyl-2-pyrrolidone (NVP) with N-isopyropyl acrylamide (NIPA) has been prepared as a way to obtain new water-soluble polymers. Structure, composition and thermal behaviour of synthesized terpolymers were determined by FTIR, UV-vis, (1)H NMR spectroscopy, elemental analysis (N content), differential scanning calorimetry, thermogravimetric and differential thermal analysis, gel permeation chromatography analysis (GPC), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The terpolymer composition-structure-property relationship indicates that the semicrystalline structure of terpolymers with different reaction times, degrees of crystallinity, and thermal behaviour depends on the content of carboxyl and amide-containing monomer linkage. The antimicrobial activities the terpolymers were evaluated against pathogen bacteria: Staphylococcus aureus, Salmonella enteridis, Streptococcucs faecalis, Eschericia coil, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The antimicrobial activity was explored by the well-diffusion technique. All the studied polymers, containing biologically active moieties in the form of ionized cyclic amide and carboxylic acid groups, were more effective against Gram-positive than Gram-negative bacteria. The bactericidal effect of terpolymers against Gram negative bacteria increased with the increasing reaction times.