Canine dietary requirements and nutritional habits have changed since dogs were first domesticated. Therefore, periodontal diseases (PD) are the most common problem affecting dogs in all age groups. The aim of this study was to determine the relationship between diet type and oral health of dogs examined in veterinary clinic. To reveal the association between nutrition and oral health, two trials were held at the same veterinary practice in Istanbul-Turkey during 2016 and 2018. For the first trial; data coming from 100 patients examined, predetermined questionnaire forms were filled by the owners. For the second trial, 106 dogs that came to the clinic during 2018 were examined by veterinarians for oral health and a form was filled out for each patients. It was determined that most of dogs (Trial 1: 82.0%; Trial 2: 71.7%) were fed dry food and also most of dogs older than 4 years had oral health problems (P<0.05). No statistically significant association was determined between oral health and type of diet, gender, and home dental care in Trial 1. Also, it was observed that oral problems in dogs fed once a day were significantly fewer than those in dogs fed two or more times a day (P<0.05). However, in Trial 2, statistically significant association was determined between PD and age, type of diet, oral health (P<0.05). These results suggest that oral health problems are more likely to be seen in older animals and feeding dogs with dry food decreases the occurrence of PD.