Spatial pattern of weeds diversity are often related to local site conditions and to competitive interaction, but topographical landscape complexity may also be important for local weeds species richness. This research is aimed at investigating the effect of elevation change on species’ composition, population size and spatial distribution of weeds flora in Abha Governorate, Aseer region, Kingdom of Saudi Arabia. In the present study, a phytosociological study of weeds flora from five localities of abandoned area located at different elevations ranging between 100 and 300 m in Abha city, Aseer region, Saudi Arabia have been investigated by using seven square quadrat at each site. Each site has an area of 196 square meters. Studied sites were visited regularly during 2012-2013. The weeds were assessed quantitatively and obtained data were used to determine the following ecological parameters including prevalence, absolute frequency, relative frequency; absolute density and relative density of weeds flora in each site. Obtained data indicated that at a lower elevation, site A situated 2250 m above sea level, 63 weed species belonging to 24 different families were recorded with three dominant weeds species, Salsola kali, Ricinus communis and Opuntia ficus-indica. In site B, about 2293 m above sea level, 54 weed species belonging to 21 different families were recorded and the most dominant species found were Salsola kali and Rumex nervosus. In site C, about 2550 m above sea level, 50 weed species belonging to 22 different families were recorded and the most dominant species found were Acacia etbaica, and Setaria viridis. In site D, about 2862 m above sea level, 40 weed species belonging to 19 different families were recorded and the most dominant species found were Acacia etbaica and Euphorbia helioscopia. In site E, 2935 m above sea level, 30 weed species belonging to 15 different families were recorded and Juniperus phoenicea was found to be the most frequently occurring and densely populated weeds. The current study screened the weeds flora at different elevations and found that there is a direct correlation between species distribution and change in the height of surveyed area The altitude seems to be the most critical ecological factor in determining the richness of vegetation as well as its types.