Background: Osteosarcoma (OS) is the most frequent malignant primary bone tumor. The explicit health guarantee (GES) plan in Chile, a law that guarantees diagnosis, treatment, and rehabilitation, incorporated OS in 2014. Objectives: To describe the characteristics of the population over 15 years, with a histopathological diagnosis of OS, to define survival rate and complications, and to identify variables that affect these outcomes. Methods: A retrospective study from 2014 to 2020, including all patients affiliated with the public health system diagnosed with OS, with histological confirmation. From clinical records, we extracted demographic data, anatomical OS location, histopathological findings, admission stage, presence of metastases, treatment, complications, and survival. We determined prognostic factors by multivariate analysis. Results: 133 patients, 58.8% men, the average age was 31 years, and the most frequent location was the distal femur (34.9%). 56.4% of the patients were admitted in Enneking stage IIB, and 36.4% presented metastasis at admission. 14.3% presented complications, the most frequent periprosthetic infection (6 cases). 16% of patients evolved with local recurrence. The multivariate model showed that age and metastases at admission constitute independent prognostic variables, with a hazard ratio of 1.017 for age (p = 0.016) and 3.13 for metastases (p = 0.0000). In the subgroup analysis, patients without metastases at diagnosis had a 5-year survival of 54% versus 11% for the group with metastases. Adjusting for age, the 5-year survival for the non-metastatic and metastatic groups was 73% and 22%, respectively. Conclusion: This is our country's first demographic description study of patients with OS. In our series, the age of presentation and the presence of metastases at admission were factors that significantly affect prognosis. When adjusting for age, the survival percentages are comparable to those reported in other international centers specialized in sarcomas.