Pediatric patients with cancer, although rarely, do present to emergency departments for first-time diagnosis, as well as for complications of treatment. The presenting symptoms can be vague, so emergency physicians must maintain a high index of suspicion and be aware of guidelines to help direct appropriate care after an initial diagnosis. It is also necessary to know the complications of treatment. Although these patients often seek care in the institution where they receive treatment, many live far from these locations and may present to any emergency department in extremis.