To explore the role of ultrasound in the diagnosis of extrahepatic cholestasis in dogs, an experimental extrahepatic cholestasis was done successfully in seven male mongrel dogs via common bile duct ligation that mimic natural cases in dogs. All observations and changes were recorded post- operative; clinical, biochemical and ultrasonography. All dogs showed jaundice, orange colored urine and clay feces in the 3rd day post-operative. Significant increase in serum levels of AST, ALT, GGT, ALP, total and direct bilirubin post-operative started from the 3rd day till reaching the peak in the 2nd week, then declined again from the 3rd week post-surgery till reaching the lowest level at the 8th week. Meanwhile, there was a significant decrease in both total protein and albumin started from the 3rd day post-ligation and remained till the end of the study. Ultrasonography of biliary system showed significant dilatation of gallbladder and common bile duct starting from the 3rd day post-ligation till reaching the maximum in the 2nd week that showed a slight reduction in their diameter from the 3rd week and reached the lowest diameter in the 8th week post-ligation. Post mortem examination showed jaundice, emaciation, as well as gallbladder and common and cystic duct dilatation. Histopathology of liver showed subcapsular hemorrhage, congestion of central vein with vacuolation in hepatocytes and yellowish brown granules of bile pigment inside other hepatocytes. In conclusion, the usage of biochemical analysis and ultrasonography is very important in early diagnosis of extrahepatic cholestasis as the changes appeared within 3 days after obstruction