Background Children with cancer are at risk of treatment related gastrointestinal toxicity and malnutrition. Intestinal dysfunction may preclude or limit use of enteral nutrition, and parenteral nutrition (PN) may be required. Published indications for PN use in children with cancer are generally nonspecific. We sought to describe patterns of use, indications, and frequency of PN prescription in children with cancer and propose indicators to guide appropriate PN use. Methods Retrospective chart review of children with cancer receiving inpatient PN in a tertiary referral pediatric hospital over 12 months was performed using electronic medical record search and paper records. Data were summarized using descriptive statistics. Results PN was prescribed to 88 patients in 111 episodes. Total use (2377 days) represented 24% of annual inpatient days in all children with cancer. Primary clinical indications were mucositis (40%), feed intolerance (29%), postoperative (16%), or “other” (15%), (including nasogastric tube refusal (n = 6)). Patients with hematological cancer had longer median episodes (19 vs 12.5 days) and earlier commencement of PN after diagnosis (50 vs 80 days) than children with nonhematological cancer. Most PN episodes longer than 28 days were in children with hematopoietic stem cell transplant (HSCT). Conclusion Inpatient PN use is common in childhood cancer. Indications include mucositis, feed intolerance, and surgical management. Patterns of use are influenced by cancer diagnosis and treatment, with greater use in children with hematological cancer and HSCT. Improved understanding and specific indications may guide appropriate PN prescription and minimize unnecessary risk, cost, and inconsistency in care.