ABSTRACT The study was carried out to determine the clinical course and epidemiological pattern of intestinal nematodes in dogs in Upper Egypt, and their impact on various hematological and biochemical parameters. A total number of 120 dogs (Age =1 month to 3 year), both sex and of different breed’s size (small and large) were included in the present study. Parasitological, clinical, hemato-biochemical and epidemiological examinations were conducted. Microscopic analysis of fecal samples (n=120) revealed three types of intestinal nematodes: Toxocara canis (n= 28), Toxascaris leonina (n =5), Ancylostoma caninum (n = 4) and mixed infection of Toxocara canis and Dipylidium caninum (n =2) with an overall infection rate 32.5% (39/120). Toxocara canis was predominate type of nematodal parasite infection in the studied population (23.3%). Puppies (0-3 months) were greatly affected with intestinal nematodes (54.8%), in particularly Toxocara canis (45.2%). Infected puppies showed off food, pale mucous membrane diarrhea abdominal bloating with potbellied appearance and vomiting. Other group of examined animals (n= 54) showed no clinical signs (asymptomatic) however a portion of this group (25.9%) was infected suggesting that absence of clinical symptoms was not an evidence of the absence of infection. Sex and breed showed non-significant differences (P>0.05) on infection rate of intestinal nematodes but season had high impact on nematodal infection The infection rate showed significant (P0.05) increasing in winter (42.3%) and autumn (43.8%) with a maximum infection rate reported in December (60%) and January (56.5%). Hematological data generated from 35 blood samples of infected and 40 samples of healthy dog populations showed significant decrease (P>0.05) in erythrocytic parameters (RBCs, Hb, PCV) and platelets count in infected group, whereas group differences for TWBCs, neutrophils, monocytes, lymphocytes, eosinophils and basophils were non-significant high. Biochemical data generated revealed significant decrease (P >0.01) in the value of serum total protein in infected group. Liver enzymes showed significant increase (P>0.01) in serum AST, ALT and ALP in infected group compared with healthy one. In conclusion, intestinal nematode in dogs was common in Upper Egypt with infection rate of 32.5% and Toxocara canis was the most common nematode infection (23.3%). They have significant effects on hematological and biochemical parameters suggestin g their importance as a health problem in dogs.