Background Diet plays an integral role in the maintenance of oral health, but dietary modifications due to medical problems such as phenylketonuria (PKU) can have adverse effects on oral health. This descriptive study was performed to evaluate the oral health status of children with PKU. Methods One hundred and ninety-seven patients with PKU aged between 1 and 22 years were evaluated. Clinical evaluations were performed by one experienced dentist regarding dental caries, gingival health and dental erosion. Categorical variables were assessed with descriptive statistics. Differences in feeding frequencies and sociodemographic characteristics were compared regarding dental caries using chi-square (χ2) tests. Results One hundred and thirty-two patients (67%) had dental caries. The mean plaque index (PI) and gingival index (GI) values were 1.37 ± 0.58 and 1.40 ± 0.64, respectively, which shows moderate plaque accumulation and moderate gingival inflammation. Of the patients, 85.3% did not brush their teeth regularly and 90.4% had never visited a dentist before. No statistically significant differences were found in dental caries according to feeding frequencies (p = 0.448). Conclusions Despite the high prevalence of caries in patients with PKU, most had never seen a dentist. Physicians must encourage patients with PKU and their parents to have regular dental visits to maintain an optimal general and oral health.