This study was done to determine the prevalence of gastrointestinal helminthes infection of stray dogs in Tabriz. Within eight months in six areas susceptible to infection in the vicinity of Tabriz, one hundred and two stray dogs (between 1-4 years old) were caught by strychnine poisoned meat and were necropsied. Fifty nine dogs were male and forty three dogs were female. For preventing to zoonotic aspects, after necropsy, digestive system of the dogs (from esophagus to rectum) were separated from body and were placed in formalin for three months. All of parasites in their digestive system were isolated. After fixation of the samples in 10% formalin their identification were performed based on parasitological characteristics. Total infection rate in stray dogs was 64.5%. In parasitological study four nematode: Toxocara canis (26.9%), Ancylostoma caninum (0.8%), Toxocara leonine (20%) and Uncinaria stenocephala (35.6%) and two cestod: Echinococcus granolosus (48%) and Taenia hydatigena (3.6%) and one Acanthocephala: Macrocanthorynchus hirudinaceus (13.9%) were identified. Maximum number of parasites in one animal belonged to Echinococcus granolosus (23.2 worms). There was not any significant difference in infection rate between males and females. However, with regard to age, it seems that older animals are more prone to acquire the infection. Furthermore, results of the study showed that because of high prevalence of digestive helminthes in stray dogs and the risk of human and livestock animal's infection a control program must be carried out for controlling and collecting of these animals to improve hygiene.