Parthenium hysterophorus, one of the “worst weeds”, is an erect and much branched annual or ephermeral herb causing colossal loss in terms of economic, environmental, animal and human health hazards. A survey on occurrence of the natural enemies of P. hysterophorus L. was conducted in Kurukshetra and its adjoining areas, Haryana, India. The Parthenium population at different places during different seasons were found to have various diseases. The native pathogens of Parthenium hysterophorus were studied and compared on the basis of pathogenicity by Koch’s postulates. A total of twenty six pathogenic fungi, P1-P26 were isolated from different diseased Parthenium plants. All the isolates were preliminarily identified on the basis of cultural and morphological characteristics and it was observed that all of them belongs to the fungi imperfecti except isolates P19, P20 which belongs to Ascomycota. On the basis of pathogenicity, the isolates P2, P5, P7, P9, P12, P17 and P23 were selected and the effect of different media on the growth and sporulation of selected pathogens was tested. This study will help to develop mycoherbicides by using these fungal pathogens in combination or single.