Parthenium hysterophorus an annual herbaceous weed, is known for its vigorous growth and as a causative agent for contact dermatitis, hay fever and diarrhea in humans and systemic toxicity in livestock. However, in spite of all the problems associated with this weed, it has been reported to have pharmacological activities. The objective of this study is to evaluate the potential of Parthenium hysterophorus leaf extracts for the synthesis of zinc oxide nanoparticles and their antimicrobial properties. Nanoparticles were extracted with the help of aqueous, methanolic and ethanolic solutions of P. hysterophorus leaves. Since a higher yield of nanoparticles was observed when synthesised using aqueous extract therefore these were used in further experiments. Synthesised nanoparticles were characterised using UV-Vis spectroscopy with maximum absorbance peak at 400 nm. SEM and TEM analysis revealed that the particles were spherical and cylindrical in shape with average particle size ranging from 16-45 nm. The chemical group association and elemental composition of nanoparticles was analysed using FTIR and SEM-EDX. Green synthesized zinc oxide nanoparticles were evaluated for antimicrobial activities against Gram positive and Gram negative bacteria. Zinc nanoparticles exhibited maximum zone of inhibition against Enterobacter aerogenes (36 mm) while least activity was seen against Staphylococcus aureus and Bacillus subtilis.