Abstract Purpose: Epithelioid hemangioendothelioma (EHE) is a rare vascular cancer with pathogenic TAZ–CAMTA1 (calmodulin-binding transcription activator 1) operating as an oncogenic driver through activation of the MAPK pathway. Trametinib is an inhibitor of MEK, a critical kinase in the MAPK pathway. We sought to evaluate the effect of trametinib in patients with EHE. Patients and Methods: A phase 2 trial of trametinib was conducted in patients with locally advanced or metastatic EHE. Eligibility requirements included evidence of tumor progression or presence of EHE-related pain requiring opiates for management before enrollment. The primary endpoint was objective response rate (ORR) as per RECIST1.1 in cases with TAZ–CAMTA1 confirmed by fusion-FISH. Secondary objectives were to estimate ORR for all patients, median progression-free survival (PFS), 2-year overall survival (OS) rate, patient safety, and change in patient-reported global health and pain scores per PROMIS questionnaires. Results: 44 patients enrolled and 42 started trametinib. TAZ–CAMTA1 was detected in 27 tumor samples. The ORR was 3.7% [95% confidence interval (CI), 0.094–19.0], median PFS was 10.4 months (95% CI, 7.1–NA), and 2-year OS rate was 33.3% (95% CI, 19.1–58.2) in the target population. Median pain intensity and interference scores improved significantly after 4 weeks of trametinib in patients using opiates. Common adverse events related to trametinib were rash, fatigue, nausea/vomiting, diarrhea/constipation, alopecia, and edema; one grade 5 ARDS/pneumonitis was related to trametinib. Conclusions: Trametinib was associated with reduction in EHE-related pain and median PFS of more than 6 months, providing palliative benefit in patients with advanced EHE, but the trial did not meet the ORR goal. See related article by Xxxxx et al., p. xxxx