District Lakki Marwat is a highly rich profile and diverse flora in southern districts of Khyber Pakhtunkhwa, Pakistan. The present study was conducted during 2018-19 in Tehsil Sarai Naurang District Lakki Marwat in order to investigate the taxonomic diversity and medicinal importance of weeds flora. A total of 42 weed species belonging to 20 families were investigated from research area. The dominant families in terms of species richness were Asteraceae and Poaceae with 6 species (14.28%) each, followed by Brassicaceae and Papilionaceae with 4 species (9.52%), Apiaceae and Solanaceae with 3 species (7.14%), Amaranthaceae and Polygonaceae having 2 species (4.76%), while remaining families (Apocynaceae, Asclepiadaceae, Asphodelaceae, Chenopodiaceae, Convolvulaceae, Euphorbiaceae, Fumariaceae, Lamiaceae, Malvaceae, Oxalidaceae, Plantaginaceae and Salvadoraceae) have 1 specie (2.38%) each. Based on plant parts used, leaves were the topmost part used of 21 species (50%), followed by whole plant 18 species (42.85%), seeds of 9 species (21.42%), stem of 8 species (19.08%), root of 5 species (11.90%), latex, shoots of 2 species (4.76%) and flowers of 1 specie. The most significant number of plant species that helped alleviate digestive problems was 12 (58.57%) of the total, followed by intestinal problems with 8 species (19.04%), abdominal pain with 7 species (16.66%). Different quantitative indices like Use Value (UV), Relative Frequency Citation (RFC) and Family Important Value (FIV), were used to find out comparative signficiance of plant species. The species with high Used Value were Mentha longifolia 0.93, Coronopus didymus 0.90, Sonchus asper 0.89. Calotropis procera 0.22, Euphorbia helioscopia 0.21, Cynodon dectylon 0.20 are species with high RFC. The Families with high FIV were Poaceae 74.7, Astercaeae 69.9, Brassicaceae 50.7, Papilionaceae 39.7 and Solanaceae 35.6.