An investigation of early lamb mortality at 20- 30 days of age was conducted in sheep flocks at Hosh-Issa in El- Bohaira Governorate, Egypt. Study undertaken in 2020/21 in which lamb deaths were repeated in the same flock at the same time of year during July–September and January–March, particularly in lambs average month of age .Knowledge of actual causes of death are important to know the causes of lambs mortality, and for taking preventive measures at the flock. This paper reports on the postmortem findings in 6 lambs out of 18 lambs that died at 20-30 day of age during July–September and January–March in the same flock (n=70).The most frequently identified causes of death were infectious diseases as septicemia, pneumonia  and gastrointestinal infections., The results showed that different species of fungi were isolated Aspergillus flavus, Aspergillus  niger, Candidia albicans, Candida famata and Candida tropicalis  were  isolated from all septicaemic cases. the most common bacterial agents obtained from all cases of infection  were Closteridium species, Coagulase negative Staphylococcus (CNS) and  Escherichia coli were isolated. Antibacterial and antifungal sensitivity of different bacterial and fungal isolates were done by using disc diffusion test for measurement of the susceptibility of bacteria and fungi to antibacterial and antifungal drugs. Histopathological changes in the internal organs  were recorded. In this study, the main causes of lamb mortality were bacteria accompanied by fungal infection especially Candida albicans which may cause gastro- intestinal candidiasis in animals. Most deaths occurred at 20-30 days of age, suggesting that events related to lambing and the immediate post-lambing period are critical for lamb survival.