Canine parainfluenza virus (CPiV) is one of the most common organisms isolated from dogs with signs of infectious tracheobronchitis (ITB). Distribution is apparently worldwide. Although CPiV may cause mild clinical infections, clinical diseases is expected to be more severe in dogs co-infected with bordetella bronchiseptica than with any these agents alone. The present study was conducted to determine the prevalence of Canine parainfluenza virus infection in urban dogs of Ahvaz area, southwestern Iran. The urban dogs were selected between referred dogs (companion) to Veterinary Hospital of Ahvaz University. Sample of respiratory secretions was collected randomly from 76 affected dogs between June 2008 and May 2009. The studied dogs were divided into two age groups (6 months) and based of environment into two groups (close and open) also. The results were analyzed by using Chi-square analysis and Fischer's exact test. Prevalence to Canine parainfluenza virus antigens was 5.3% (4 of 76) by means of immunochromatography indicating that this antigen is present in the ecosystem. The infection had more prevalence in those dogs that were in open environment (17.65%; 3 of 17) in compared with close environment (1.69%; 1 of 59) and the difference was significant between different groups (P= 0.033). Prevalence was more in dogs less than 6 months (6.82%; 3 of 44) in compared with dogs above 6 months (3.12%; 1 of 32), but the difference was not significant between two groups (P= 0.436). Prevalence of infection was 4.44% (2 of 45) in male dogs and 6.45% (2 of 31) in female dogs. Prevalence was 6.06% (2 of 33) in Mixed breed, 5.55% (1 of 18) in Germanshepherds and 11.11% (1 0f 9) in Doberman pinchers. There was no significant difference between different sexes and breeds also (P>0.05). This study showed that Canine parainfluenza virus can be as a risk factor particularly for those dogs are in contact together in open environment and kennel dogs in Ahvaz area.