The present investigation was carried out to study the skin histopathological changes of Oreochromis niloticus after 5 hours transportation stress in water with and without sodium chloride (NaCl). Three groups were used in an extreme five-hour transport mode: the control group (not transported - CG), post-transport group without salt (PT-S), and post-transport group with 5gm/L salt (PT+S). The skin tissue from the Nile tilapia PT-S group showed a flattened and thin epidermal layer with a loss of goblet cells. There was marked mononuclear inflammatory cellular infiltration around blood vessels (vasculitis). The dermal loose connective tissue lost its tight appearance and had gaps. The lower compact dermal fibrous connective tissue layer showed
irregular less compact collagenous fibers. The muscular layer beneath the dermis exhibited significant interstitial myositis with inflammatory cellular infiltration. While skin tissue from the Nile tilapia PT+S group showed marked improvement in the histologic skin tissue structure including the epidermis, dermis, hypodermis and muscular layers. The improvement in epidermal
layer showed normal epithelial cells and regular collagenous bundles of dermal layer and normal hypodermis. Conclusion: Our findings have significant importance in the field of fish aquaculture and address the importance of skin and its mucous cover health during transportation, we recommend the use of salt during transport of O. niloticus as the benefits of it using during
transport appear to reduce the effects of transport stress.