(1) Background: The aim of our study was to evaluate parental stress after 6 and 12 months of a ketogenic diet, considering demographic and clinical variables (epilepsy type, epilepsy duration, seizure number, antiseizure medications, comorbidities, efficacy, and adverse events). (2) Methods: We consecutively enrolled 36 children aged between 3 and 10 years who had been diagnosed with various types of drug-resistant epilepsy and who were in therapy with a ketogenic diet for better seizure control. A standardized neuropsychological questionnaire (Parenting Stress Index-PSI) was administered to the parents evaluating parental stress at baseline (T0), after 6 (T1) months, and after 12 months (T2). (3) Results: After 6 and 12 months of dietary treatment, Parental Distress and Total Stress mean scores were statistically significantly increased. Post hoc analysis showed no significant changes in the scores between T0 and T1, although there was a significant increase between T1 and T2. We did not find statistically significant relationships between parental stress and the other variables considered. (4) Conclusions: The ketogenic diet can be challenging for parents and can affect the perception of parental stress, especially in the long term. Parents may feel inadequate in their role; therefore, they should be helped and encouraged through additional supports in order to maximize the adherence to diet therapy.