Study was done on impact of invasive alien weeds Chromolaena odorata and Parthenium hysterophorus on native naturalized flora of few selected sites in Mysore, Karnataka. Total six sites were selected for the study. Of which, at 3 sites C. odorata and P. hysterophorus were present (sites 1, 2 and 3) while at other 3 sites C. odorata and P. hysterophorus were absent (sites 4, 5 and 6). At sites 1, 2 and 3, frequency, density and abundance of the native flora were low than the sites 4, 5 and 6. There was 30, 24 and 12% reduction of native flora at sites 1, 2, and 3, respectively. There was a constant fear of losing many medicinally and economically important plants due to invasion of these weeds.