The widespread use of antibiotics has led to an increase in the number of strains resistant to major antibacterial pharmaceuticals. Many synthesized quaternary ammonium compounds possess antibacterial, antifungal and antiviral properties. Incorporation of quaternary ammonium moieties into dendrimers represents a promising strategy for the preparation of novel antimicrobial biomaterials. Here, poly(quaternary ammonium) chloride dendrimers were synthesized by functionalizing poly(propylene imine) (PPI) dendrimer with various lengths of alkyl chains. In vitro antimicrobial assays indicate that the amphiphilic dendrimers are potent antimicrobial agents with activity against multidrug-resistant pathogens such as the methicillin-resistant Staphylococcus aureus.