In Egypt and during the last 50 years, several changes in agricultural practices have affected different components of agro-ecosystems including weed flora. The aim of the present study was to evaluate changes in the weed flora of El-Menoufia Governorate, South of the Nile Delta of Egypt during the period from 1984 to 2018, in response to different agricultural practices. A total of 240 stands were investigated in both spring and summer seasons in order to document the present status of the weed flora. The obtained results were compared to results obtained by other authors in 1984. Results showed major shifts in the weed flora of El-Menoufia Governorate where 67 species out of 146 species were recorded in our study while only 42 species out of 121 species were present in 1984 survey. Changes in the family composition, life form, life span, and chorology were reported. Reasons responsible for such changes have been discussed. Changes in the crop composition, cultivation area of each crop, excessive use of fertilizers and pesticides, changes in irrigation water quality and quantity are the leading change promoters. The high economic importance of the weed flora and the potential threats facing agriculture in Egypt necessitate the formulation of a sustainable strategy for maintaining agro-ecosystems of Egypt and its biodiversity.