The survey was conducted in the farmers’ field of Durba Chara village of Gauripur upazilla under Mymensingh district to find out the floristic composition of weeds in three crops i.e. summer rice, potato and winter rice under T. aman-potato-boro cropping pattern. Five farmers’ fields were surveyed by using a quadrat of 0.5m × 0.5m size in four spots from each field randomly. The data were summarized using frequency, field uniformity, mean field density and relative abundance. A total of 27 weed species belonging to 11 families were found in T. aman, potato and boro rice, of which 22 species were under 11 families in T. aman, 15 species under seven families in potato and 20 species were under nine families in boro rice. Echinochloa crusgalli was the most abundant weed in both potato and boro rice while in T. aman, Ludwigia hyssopifolia dominated over others. Echinochloa crusgalli and Polygonum hydropiper were common in both potato and boro rice. The other three dominant weed species i.e. Cyperus rotundus, Cynodon dactylon and Panicum distichum in potato and Eclipta alba, Cyperus difformis, Eleocharis atroperpurea in boro were completely different from each other. In T. aman, five completely different weed species i.e. Ludwigia hyssopifolia, Alternanthera sessilis, Polygonum orientale, Fimbristylis miliaceae and Hedyotis corymbosa were found dominant. Broadleaf weeds were dominant in both T. aman and boro but in potato, grasses dominated over others.