One hundred samples of Tilabia nilotica were collected from different markets in Dakahlia Governorate to evaluate their bacteriological quality by determine Psychrotrophic counts. The effect of these foodborne bacteria on chemical quality of fish and consumer health were studied. The bacteriological examination revealed that the mean value of total Psycrotrophic count, total Pseudomonas and total Bacillus cereus count in Tilapia nilotica samples were 3.1 × 10²  ±1.8× 10²  cfu/ gram, 5.1× 10³±1.4 × 10²cfu/ gram and 4.0×10³±2.6 × 10²cfu/gram respectively. Biochemical tests as Histamine (H), Thiobarbituric acid (TBA),Total volatile basic amines (TVBN) were measured to determine the quality of examined fish and their effect on health of consumers. The obtained results revealed that, the minimal and maximal histamine(H) content were 5.7 and 24.6 mg% respectively, 10.2 &25.1 mg/100gm for minimal and maximal (TVBN)respectively and 0.534 & 0.988 mgDK/Kg for minimal and maximal (TBA) content in examined fish samples