Background: With improved long-term health outcomes and survivorship, 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 examine the diet quality of children receiving treatment for cancer. Methods: Participants were parents of children with cancer who were receiving active treatment and not receiving supplementary nutrition. A 24-h 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). Most 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: Children receiving cancer treatment are consuming diets of reasonable quantity, but poor quality. 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.