Background: In phenylketonuria (PKU), only a limited range of natural foods, such as fruits, vegetables, oils and sugars, can be consumed without restrictions. The present study aimed to study if food neophobia (i.e. an unwillingness to eat novel food) occurs in patients with PKU and to compare in non-PKU healthy controls and to identify any associated factors. Methods: This cross-sectional case-control study used a convenience sampling strategy to recruit patients diagnosed with PKU and healthy controls matched by gender and age. Patients and controls were invited to complete the food neophobia scale (FNS) questionnaire, and clinical and treatment data were collected through a review of medical records. Results: Twenty-five patients (mean age 19.3 ± 4.7 years, 13 women) with PKU and 25 controls (mean age 19.9 ± 4.9 years; P = 0.676, 13 women) were evaluated. The mean age of treatment onset in patients with PKU was 52.8 ± 29.7 days. The mean phenylalanine (Phe) level in the 12-month preceding neophobia study was 710.5 ± 346 µmol/L. The mean FNS score of patients with PKU was significantly higher (47.2 ± 9.7) than controls (29.4 ± 12.5, P < 0.001). Food neophobia was associated more with male gender (P = 0.039). Conclusions: Food neophobia is frequent in patients with PKU. It does not appear to be associated with female gender, with Phe levels and not just in children.