Weeds is the biggest challenge for pineapple production as competing for natural properties such as nutrient, water, sunlight, shelter and others which provided for the pineapple and also act as a host for pest attack. Improper weed management could cause severe weed infestation and reduce pineapple yield specifically in peat soils compared to mineral soils. Peat soils has excellent moisture holding, aeration and physical characteristics for weed germination. Since weed germination was influenced by agronomic changes, this study was conducted to examine weed species composition infested peat soils due to very limited study pertaining this issue. Study was carried out at three different peat areas of pineapple fields in Mukim Ayer Hitam, Muar, Johor. Experiment was done according to the quantitative survey method by using standardized quadrat. Surveying was done several weeks upon herbicides spraying. Broadleaves dominated peat areas compared to grasses, sedges and ferns at all sampling locations. Asystasia gangetica was found as most dominant weed species recorded more than 40% in peat soil regardless the surveyed locations. Asystasia gangetica adapted well in peat soil due to creeping root that remain robust. Proper documentation of dominant weed species infested pineapple plantation particularly in peat soil will be the key tool for sustainable weed management.