Chemical modification of poly(vinyl chloride), PVC, was performed via its substitution reaction with 6-amino-2-thioxo-tetrahydropyrimidin-4-one (1) and three of its derivatives (1A-C). The chemical structures of the modified PVC samples have been confirmed via FTIR and 1HNMR spectroscopic analyses. Photostability of the modified PVC were investigated by following the rates of dehydrochlorination of the 6-aminopyrimidine derivatives modified PVC samples conductometrically in comparison with both blank PVC and that stabilized with 2-hydroxy-4-(octyloxy)-phenyl-benzophenone as reference UV absorber. Moreover, thermal stability as well as physicomechanical properties of all investigated PVC samples have also been determined. Modified PVC samples exhibited enhanced photo and thermal stability as well as mechanical properties when compared to the blank unmodified sample. Antimicrobial properties of the tested PVC samples were explored against Gram +ve bacteria (Staphylococcus aureus), Gram -ve bacteria (Escherichia coli) as well as A. flavus and C. albicans as fungi. However, incorporation of 6-aminopyrimidine derivatives to the PVC backbone chains enhanced their inhibitory effect against the examined microorganisms.