Purpose. To determine short-term changes in intraocular pressure (IOP) after intravitreal injection of 0.1 mL pegcetacoplan (Syfovre; Apellis Pharmaceuticals) for the treatment of geographic atrophy (GA). Methods. This prospective, interventional study evaluated a case series of patients with GA without corneal pathology or a history of vitreoretinal surgery who received pegcetacoplan injections. IOP was measured with a handheld applanation tonometer immediately prior to injection, immediately after injection, and at 5, 10, 20, and 30 minutes postinjection. Results. Fifty-one patients (total 73 eyes) were enrolled. The mean (±SD) preinjection IOP was 15.3 ± 3.3 mm Hg, which significantly increased to 40.2 ± 13.7 mm Hg (P < .001) immediately after injection. Subsequent IOP measurements showed a gradual decrease to 31.3 ± 11.6 mm Hg at 5 minutes (P < .001), 23.2 ± 9.7 mm Hg at 10 minutes (P < .001), 19.6 ± 8.6 mm Hg at 20 minutes (P < .001), and 16.4 ± 4.9 mm Hg at 30 minutes (P = .05) postinjection. No further treatment was required, except that the left eye of 1 patient with a history of primary open-angle glaucoma and persistent IOP elevation underwent anterior chamber tap 20 minutes after injection. Multivariate linear regression analysis revealed that a higher IOP at 30 minutes postinjection was significantly associated with the preinjection IOP (P = .004) and with a history of glaucoma (P = .019). Conclusions. Following pegcetacoplan injections, immediate IOP elevation was observed, which gradually declined within the first 30 minutes. Eyes with higher baseline IOP or a history of glaucoma exhibited higher postinjection IOP.