The current study aimed to determine organochlorine pesticides (OCPs) residues in muscle tissues of Tilapia (Oreochromis niloticus) with different weights collected randomly from different localities at Cairo and Giza markets by Gas Chromatoghraphy. The total mean values of DDT, DDD, DDE, Endrin, Dieldrin, Endosulfan, γ-chlordane, δ-BHC, Hepatochlor epoxide, Methoxychlor and Hepatochlor residues in the examined samples of tilapia were 16.82 ± 4.7, 44.80 ± 4.65, 8.34 ± 1.42, 26.54 ± 3.13, 10.91 ± 2.72, 6.20 ± 1.17, 21.32 ± 3.44, 16.17 ± 3.07, 5.33 ± 10.67 , 1.24 ± 0.31 and 1.28 ± 0.31 ng/g, respectively. Accumulation of organochlorine pesticides in fish tissues was related to rate of pollution, lipid content, feeding behavior, rate, size and age. There were significant differences between organochlorine pesticides residues and different weights of tilapia. Most of the examined samples were within the maximum permissible limits of pesticides residues according to US-FDA (2008) and Codex Alimentarius Commission (1996) and should not pose a health risk to consumers. The public health hazards of organochlorine pesticides residues were discussed.