The fast development of banking sector brings banks facing higher risk exposure; the level of capital adequacy of banks attracts our attention again. This study will investigate the determinants of capital adequacy ratio (CAR) which measures banks’ safety and soundness. Most of the previous studies only focus on one single market; this study extends the previous literature by studying East Asian regions, so that the results could be more representative. Factors are divided into two categories: internal factors (bank-specific factors) and external factors (macroeconomic indicators). It is found that among the internal factors, loan ratio, profitability and leverage level are significant determinants of CAR while among the external factors, GDP growth rate and average market CAR have significant impact on CAR.