<p>Insects play a vital role in the pollination of both wild and cultivated plants around the world. Mustard (<i>Brassica juncea</i>) is a major oil-producing crop in Bangladesh, where small-scale farmers grow a variety of crops, but knowledge of mustard pollination requirements is scanty. We surveyed insect visitors and their abundance in mustard fields using transect walks and colored pan traps. Our findings revealed that a wide range of bee, fly, and butterfly species visited the oilseed mustard flowers, with <i>Apis mellifera</i> being the most common visitor and also an efficient pollinator. We also found that yellow pan traps were most effective for monitoring insect visitors in oilseed mustard fields, followed by white pan traps. We measured the contribution of insect pollination to pods per plant, seeds set per pod with and without flower visitors using net bag at four locations. According to the insect exclusion experiment, 9.72% of pod set and 47.93% of seed set reduced in the absence of insect pollinators. These results clearly demonstrated that, in oilseed mustard, insect pollination is necessary to get large seed yield. Our research findings highlight the importance of insect pollinators to enhance oilseed mustard production and encourage farmers to safeguard the insect pollinators in Bangladesh for increasing the yield of this crop.</p>