Background: Parthenium hysterophorus L. (Family Asteraceae, local name Chatakchandni), an invader weed, assumes importance and poses a problem because of its nuisance value. The present study accounts for its population structure, community relation and its probable association with neighbour species within the major grassland vegetation types of the region. Materials and Methods: For the study of population status, phytosociological characters, neighbour relations of Parthenium and its contribution to the two major grasslands’ the managed and natural were calculated by the standard sampling methods. Results: Highly disturbed or completely cleaned sites may be fast colonized and aggregated by Parthenium, as evident from the values of its phytosociological attributes. In natural grassland, however, the number of species as the nearest neighbour of Parthenium was quite high. Parthenium was found to occur at all different stages of growth and at every stage of its life cycle throughout the year. In the months of July, November and March, a much greater number of individuals were in the seedling stage. Conclusion: Since there is no lapse period between seed dispersal and germination, effective management may be exercised only before they enter the reproductive phase. Since there is no mode of asexual regeneration in this species, manual elimination must be held at juvenile stage to get an area rid of this noxious weed.