This work was designed to investigate incidence of Aeromonas  hydrophila in non hatched chicken eggs and study its pathogenic effect on embryonated chicken eggs. Four hundred non hatched chicken eggs were collected, (200) samples from mechanical hatchery and (200) from balady hatchery in Assiut governorate. Thirty (7.5%)  A. hydrophila isolates were isolated, 14 (7%) and 16(8 %) from the mechanical hatchery and balady hatchery respectively. Inoculation of A. hydrophila strain via yolk sac route in a dose of 1.5x 10⁷/ ml induced 100% embryonic mortalities after 3 days. Re-isolation of A. hydrophila from liver and yolk with a percentage 90% and 95% respectively . Groups of  5 days –old and  17 days –old ECE dipped in media contain A. hydrophila in a dose 6.1X 10⁹ /ml induced 25%and 30% embryonic mortalities after  7 and 4  days respectively , the  re-isolation of A. hydrophila was 60%,33.3% from  liver and 80% ,83.3% from  yolk respectively. Hatchability was 75% and 70% in dipped groups. The rate of A. hydrophila re-isolation from organs of sacrificed hatched chickes (intestine, liver, heart and yolk sac) was 93.1, 68.9, 17.2 and 51.7%, respectively. Histopathological changes in liver, heart and intestine were hepatic degeneration, myocardial congestion and intestinal heamorrhages.