A new N-halamine monomer, N-chloro-2,2,6,6-tetramethyl-4-piperidinyl methacrylate (Cl-TMPM), was synthesized and used to prepare water-based polymeric N-halamines by emulsion polymerization. The chemical structures of the samples were characterized with Fourier transform IR, (13)C NMR, UV/vis, and differential scanning calorimetry analyses. Upon the addition of a small amount of the polymeric N-halamine latex emulsions into commercial water-based latex paints as antimicrobial additives, the new paints provided potent antimicrobial activities against Staphylococcus aureus (S. aureus; Gram-positive bacteria), methicillin-resistant S. aureus (MRSA; drug-resistant Gram-positive bacteria), vancomycin-resistant enterococcus (VRE; drug-resistant Gram-positive bacteria), Escherichia coli (E. coli; Gram-negative bacteria), Candida tropicalis (C. tropicalis; fungi), MS2 virus (15597-B; virus), and Stachybotrys chartarum spore (S. chartarum; mold), and they successfully prevented biofilm formation and development. The antimicrobial functions of the new paints were long-lasting for more than 1 year under normal in-use conditions, easily monitorable by a simple potassium iodine/starch test, and readily rechargeable if the functions were accidentally lost as a result of challenging conditions such as heavy soil, flooding, etc.