Objectives: Sodium zirconium cyclosilicate (SZC) is a selective potassium (K+) binder for hyperkalemia, which received regulatory approval in Korea in November 2025. This post-hoc subgroup analysis of the phase 3 HARMONIZE-Global study (NCT02875834) evaluated the efficacy and safety of SZC specifically in Korean patients to establish clinical evidence for its use in Korean patients and support localized treatment strategies. Methods: Korean patients with hyperkalemia (serum K+ ≥ 5.1 mmol/L) were included in this phase 3, randomized, double-blind, placebo-controlled study. Following open-label treatment with SZC 10 g three times daily during a 48-hour correction phase, patients achieving normokalemia (3.5–5.0 mmol/L) were randomized to maintenance treatment with SZC 10 g, SZC 5 g, or placebo once daily for 28 days. The primary endpoint was mean serum K+ during Days 8–29 of the maintenance phase. Results: In the Korean subgroup (n=121), 84.3% of patients had chronic kidney disease and 78.5% were receiving RAAS inhibitors at baseline. During the correction phase, mean serum K+ significantly decreased by 1.32 mmol/L at 48 hours compared to baseline (p < 0.0001), with 90.9% of patients achieving normokalemia. During the maintenance phase, SZC effectively maintained normokalemia; the least square mean serum K+ was significantly lower in the SZC groups than in the placebo group (SZC 10 g: 4.51 mmol/L; SZC 5 g: 5.00 mmol/L; Placebo: 5.59 mmol/L; p < 0.001 for both). On Day 29, the proportion of patients maintaining normokalemia was significantly higher with SZC 10 g (66.7%) compared to placebo (8.7%; p < 0.001). SZC was generally well tolerated with no reported deaths. The most common adverse events were mild or moderate constipation. Conclusion: SZC demonstrated rapid correction and effective maintenance of normokalemia in Korean patients, consistent with global findings. These results support SZC as a prompt, sustained, and well-tolerated therapeutic option for hyperkalemia management in Korea.