Glioblastoma (GBM) is a malignant central nervous system neoplasm that remains largely incurable. Limited treatment options currently exist after disease progression on standard-of-care first-line therapy. However, repurposing the use of approved therapies in patients with potentially targetable genomic alterations continues to be an emerging area of interest. This report presents the first description of a patient with isocitrate dehydrogenase wild-type GBM with an underlying RET amplification who demonstrated a near-complete response while receiving therapy with the RET inhibitor selpercatinib. The case highlights the excellent blood-brain barrier penetration of selpercatinib, as well as its potential role in the management of RET-amplified GBM. Larger biomarker-enriched studies are needed to confirm the results of this case report. Given the rare incidence of RET alterations in GBM, findings from this report can help guide and support optimal treatment strategies for patients with RET-altered GBM.