The aim of this study was to investigate the prevalance of behavioral changes associated with age in dogs and their relationship to sex, reproductive status, weight, housing and feeding. About 134 dogs older than 7 years were included in this study. Owners of dogs were interviewed and gather information about signs: sleep/wake cycle, social interaction, learning and house training and disorientation. Forty seven dogs (35.07%) were found to have shown behavioural changes associated with age-related cognitive impairment. Prevalance increased with age. There were no significant effects of sex, weight, housing (inside/outside) and feeding (dry food/home made) on behavioral changes. According to categories, 20 dogs had alterations in one category, 7 dogs had two categories, 12 dogs with three categories and 7 dogs had four categories. The most impaired behavioral categories were changes in sleep/wake cycles (32%) and social interaction (30%) followed by disorientation (20%) and learning and house training (18%). The results of this study suggest that estimates of the prevalance of various degrees of age-related behavioral changes. Veterinarian and dog owner should be aware of this problem.