The total capital ratio of 19 commercial and state-run banks under the Basel III framework averaged 15.35 percent as of end-2018, up 0.11 percentage points from a year earlier, according to the Financial Supervisory Service (FSS).
It was the highest since the capital requirement by Bank for International Settlements (BIS), which gauges financial soundness, was adopted here in 2015.
The common equity tier-1 capital ratio, which measures banks' capital against its risk-weighted assets, added 0.05 percentage points over the year to 12.61 percent at the end of 2018.
The higher figures were attributed to profit gains, which led to a faster increase in capital than risk-weighted assets.
Citibank Korea logged the highest capital ratio of 19.01 percent as of end-2018, while K-Bank and Kakao Bank, the country's two Internet-only banks, posted the total capital ratios of 16.53 percent and 13.85 percent each.