Abstract: It was the aim of this study to determine the interaction between the Newcastle disease (ND) and infectious bursal disease (IBD) vaccines used to control these two important viral infections greatly affecting poultry industry worldwide. The commercially available vaccines in the Sudan were used. Haemagglutination inhibition (HI) and agar gel immunodiffusion (AGID) tests were employed to measure the Ab titres in chicks sera to ND and IBD respectively. Generally, IBD vaccine was reported to have adverse effect on the ND vaccine whereas the reverse was not true. The results obtained also revealed that better Ab responses against NDV were detected when ND vaccine was administered before IBD vaccine. The deleterious effect of IBD vaccine on Ab levels against NDV antigens was slightly (p<0.05) low when IBD vaccine is administered at two weeks as compared to three weeks of chicken age. No variations in the Ab titres when chicks were boostered with ND vaccine containing LaSota or Komorov strain of the virus at 4 weeks were observed. However, slightly (p<0.01) better Ab responses were noted for LaSota over Komorov strain. It was, therefore, concluded that vaccination of chicks with ND vaccine containing LaSota strain of the virus when they were 10 days followed by vaccination with IBD vaccine at two weeks and boostering with the same ND vaccine yielded better Ab responses but slightly lower protection levels.