Background With improved survivorship and long-term health outcomes, the long-term nutritional management of childhood cancer survivors, from diagnosis to long-term follow-up, has become a priority. The aim of this study was to assess diet quality of children receiving treatment for cancer. Procedure Participants were parents of childhood cancer patients who were receiving active treatment and not receiving supplementary nutrition. A three-pass 24-hour dietary recall assessed food and nutrient intake. Serves of food group intakes and classification of core and discretionary items were made according to the Australian Dietary Guidelines and compared with age and sex recommendations. Results Sixty-four parents participated (75% female). Nearly all children were not consuming adequate intake of vegetables (94% of patients), fruit (77%) and milk/alternatives (75%). Of the vegetables that were consumed, half were classified as discretionary foods (e.g. chips/fries). Nearly half (49%) of children exceeded recommendations for total sugar intake and 65% of patients had an excessive sodium intake. Discussion The diet quality of children undergoing treatment for cancer is generally poor. Information provided during treatment should focus on educating parents on a healthy diet for their child, the importance of establishing healthy eating habits for life, and strategies to overcome barriers to intake during treatment.