Objective: The majority of problems and symptoms occur in the gastrointestinal system in children with cancer. Parents have difficulty in coping with the nutritional problems and changing routines of children and need support in this respect. This study aimed to assess the nutritional problems of children with cancer and the information needs of their parents. Methods: This descriptive study was performed among children with cancer aged 3-18 years and their parents (n = 69). The data were collected through a data collection form developed by the researchers based on the literature. Results: The most prominent nutritional problems experienced by children were loss of appetite (85.5%), nausea (84.1%), vomiting (81.2%), fatigue (79.7%), and mucositis (66.7%). According to the parents, the factors causing these nutritional problems in children were physiological factors (100%) and the foods given to children in the hospital (65.2%). The parents mostly needed information about food-drug interactions (58.0%), food-disease interactions (52.2%), foods that children with neutropenia should avoid or should eat (neutropenic diet) (46.4%), and frequency of nutritional intake (36.2%). Conclusions: This study has shown that most children experience at least one nutritional problem, and the parents need comprehensive and regular information about nutrition. Pediatric oncology nurses have a significant responsibility in the evaluation, education, and monitoring of these children.