Aim: To report a case of new-onset glaucoma following administration of the Moderna (mRNA-1273) vaccine. Background: Previous studies have reported a low incidence of ocular adverse events induced by the coronavirus disease 2019 (COVID-19) vaccine. The literature on open-angle glaucoma associated with COVID-19 vaccination is limited. Case description: The patient complained of blurred vision 2 days following the administration of the second dose of the Moderna vaccine in July 2021. At presentation, the ophthalmic examination showed elevated intraocular pressure (IOP) of 30 mm Hg in her right eye (OD) and 18 mm Hg in her left eye (OS). There were no signs of intraocular inflammation or glaucomatous optic neuropathy at the initial presentation. She was treated with a topical β-blocker first. In addition, 1 month later, her IOPs were 28 mm Hg OD and 26 mm Hg OS. Although treated with multiple antiglaucoma medications, her optic cup-to-disc ratios were increased in both eyes (OU) compared to May 2019. She developed a glaucomatous visual field (VF) defect OD in October 2021. Optical coherence tomography (OCT) revealed progressive retinal nerve fiber layer (RNFL) thinning in OU. Conclusion: Glaucoma may be a rare but severe ocular adverse event of the Moderna vaccines. The ophthalmologist should pay attention to the risk of increased IOP following COVID-19 vaccination. Clinical significance: We reported a case of new-onset open-angle glaucoma presumably associated with COVID-19 vaccination.