To assess the impact of the Megachile bee, Chalicodoma cincta cincta on pod and seed set of Cajanus cajan L. Mill sp, its foraging and pollinating activities were studied in Yaoundé, for two seasons (September - October 2008 and July - August 2009). Observations were made on 80 inflorescences per treatment. The treatments included unlimited floral access by all visitors, bagged flowers to deny all visits, and, limited visits by C. c. cincta only. In addition, all flower visitors were recorded. The Megachile  bee’s seasonal  rhythm  of activity, its foraging behaviour on flowers, its pollination efficiency, the fruiting rate, the number of seeds per pod were recorded. Individuals from 18 species of insects were recorded visiting flowers of C. cajan in the two years. Chalicodoma cincta cincta was the most frequent, followed by Xylocopa calens, Apis mellifera adansonii, Megachile bituberculata, Camponotus flavomarginatus and Xylocopa albiceps. Apart from bees, wasps were also recorded as likely predators. Xylocopa calens mainly foraged for nectar and pollen resource. The mean foraging speed was 10.33 flowers/min. Flowers visited by C. c. cincta had higher fruiting rate compared with the others while those bagged had the lowest. In addition, seed formation was higher in C. c. cincta visited flowers compared with all others. The results show that this crop experiences pollination deficit even under normal circumstances, considering that flowers visited by C. c. cincta had higher yields compared with those under unlimited access by all visitors. The fruiting rate, the number of seeds/ pod and the percentage of normal seeds of unprotected inflorescences were significantly higher than those of inflorescences protected from insects. Chalicodoma cincta cincta foraging resulted to a significant increment of the fruiting rate by 19.65 %, as well as the number of seeds/per pod by 24.33 % and the percentage of normal seeds by 11.52 %. Conservation of C. c. cincta nests close to C. cajan fields could be recommended to improve pod and seeds production in the region.