Abstract: As infectious bursal disease (IBD), a viral disease, has no specific antiviral treatment, the use of herbal remedies with immunomodulatory and antiviral properties presents a valuable complementary approach to enhance host defenses and reduce disease severity. The aim of this study was to assess the clinical signs, morbidity and mortality rates due to Nigella sativa seed powder (NSSP) pre-administration in cockerels challenged with a very virulent IBD virus (vvIBDV). One hundred, one-day-old Dominant black marshal cockerel (DBMC) chicks were randomly divided into 5 groups (A, B, C, D and E) of 20 birds as follows: A and B were administered feed only from 1 to 42 days of age (doa); C and D administered the NSSP+feed from 21 to 27 doa; E was administered the NSSP+feed from 1 to 42 doa. All the chicks were vaccinated against ND at 7 and 17 days of age. At 28 doa, groups B, D and E were challenged with a vvIBDV orally. The chickens were monitored daily for clinical signs, and morbidity and mortality rates were calculated. Results revealed mild overall clinical sign in groups D (13.0%) and E (9.6%), and severe signs in group B (22.6%). There were lower morbidity and mortality rates in groups D (70.0%; 30.0%) and E (60.0%; 10.0%) than in group B (80.0%; 55.0%). In conclusion, pre-administration with NSSP decreased clinical signs, morbidity and mortality rates in the vvIBDV-challenged cockerels. Hence, there is need for assessment of the effects of NSSP on other parameters in vvIBDV-challenged birds.