Metastatic osteosarcoma with direct cardiac involvement is an exceptionally rare finding, with only 63 total reported cases in the English literature over the past 123 years. Although the precise incidence is unknown, we estimate that direct cardiac involvement currently occurs in <2% of metastatic osteosarcoma cases. We also find that before the adoption of adjuvant chemotherapy as a standard of care therapy for osteosarcoma, metastatic osteosarcoma to the heart was much more common than it is today, as cardiac involvement occurred in ∼20% of cases of metastatic osteosarcoma before the 1980s. This suggests that adjuvant chemotherapy has not only improved the overall prognosis of osteosarcoma, but also altered the metastatic pattern of disease. In this paper we present the case of an 11-year-old boy with metastatic osteosarcoma to the cardiac interventricular septum, as well as review 20 other previously reported pediatric cases of metastatic osteosarcoma to the heart. We also analyzed the cardiac surgical outcomes for 11 pediatric patients with metastatic osteosarcoma to the heart. The median disease-free survival time was 12 months, demonstrating that metastatic osteosarcoma to the heart is currently a rare occurrence with a poor prognosis.