<p>This study evaluates how Basel III implementation affected bank asset quality, profitability, liquidity, and financial stability across emerging markets. Using a triple difference-in-differences framework applied to 3,222 bank-year observations from 13 countries over the period 2011 to 2019, the analysis exploits variation in adoption timing and bank characteristics to identify causal effects. The results indicate that Basel III improved asset quality and liquidity but reduced profitability, with the largest costs concentrated in the early implementation period. The largest costs fell on large banks early on, while state-owned banks recorded early gains that proved difficult to sustain. These patterns suggest that regulatory outcomes depend on bank type and institutional capacity rather than on uniform compliance. The study contributes to the Basel III literature by demonstrating the conditional and phase-dependent nature of regulatory effects and by highlighting the importance of implementation sequencing and institutional readiness in regulatory policy design.</p>