In Bangladesh’s hill regions, where there is less cultivable land, increasing crop output requires efficient land use. Thus, in this challenging farming setting, two crop-based patterns evolved into three or four crop-based patterns. To increase cropping intensity and farmer income by incorporating mustard and mungbean in a rice-based cropping pattern, a field experiment was carried out at Sadar and Panchari Upazila, Khagrachhari during 2017–2018 and 2018–2019. Two years’ mean data (using a block farming approach) showed that the modified pattern had produced a much higher yield through improved management practices. In the improved cropping pattern (Transplant aman (T. aman)–mustard–mungbean–aus rice), a higher rice equivalent yield (16.25 t ha−1) was found due to the inclusion of mustard and mungbean in the existing rice-based cropping patterns T. aman–fallow–boro (9.87 t ha−1) and T. aman–fallow–tomato (9.09 t ha−1). The gross margin from the improved cropping pattern was 448,715 BDT, which was 44.26% higher than the mean gross margin (311,050 BDT) of the two existing cropping patterns. Farmers are interested in growing mustard and mungbean since both can easily cultivated in hilly areas and can yield great economic returns quickly. For the large-scale production of oil and pulse, the T. aman–mustard–mungbean–aus rice cropping pattern might be introduced in the Khagrachhari district of Bangladesh.