Infectious bursal disease (IBD) is a severe, highly contagious immunosuppressive disease. This study aimed to investigate a suspected Infectious bursal disease field infection with apparent morbidity and elevated mortality in a floor-reared Hy-line layer flock in Khartoum State, Sudan. The investigated flock showed depression, dullness, ruffled feathers, diarrhea, pasted vent, and decreased feed and water intake. The affected birds were underweight (800gm to 870gm). The mortality rate was found to be 14.7%. A post-mortem examination revealed enlarged, edematous bursae with various degrees of petechial hemorrhage in the serosal and mucosal surfaces. Hyperemia, inflammation, yellowish exudate, and atrophy were also seen in some of the affected bursae. Extremely distended ureters filled with a whitish material were detected. Enlarged kidneys with degenerative changes and obvious necrotic foci were detected grossly. Agar Gel Immuno-diffusion (AGID) tests and inoculation of the virus in chick embryos were found to be negative. Indirect IBD conventional ELISA test for VP3 for serum of 20 birds revealed 100% positive cases. Creatinine, uric acid, and urea in the serum of 22 infected birds from the diseased flock and 19 noninfected birds from the original flock showed a recognizable elevation in the three parameters that reached about 5 times, 6 times, and 2 times respectively. The presence of bursae with obvious lesions in a layer flock of 21 weeks of age was considered the main criterion for the diagnosis. The flock was diagnosed with IBD. ELISA results support the diagnosis. Infection with IBD at this age (21 weeks) could be attributed to bad management in general and bad nutrition in specific which led to being underweight and delayed the regression and disappearance of the bursa of Fabrecious.