This study employs a panel data analysis to identify the factors that significantly affect the capital adequacy ratio (CAR) of Vietnamese commercial banks for the period from 2011 to 2018. During this period, the number of banks had decreased from 41 to 31 due to mergers and acquisitions. The variables that are hypothesized to affect the capital adequacy ratio of commercial banks in Vietnam include bank size (SIZE), deposit (DEP), loan (LOA), loan loss reserves (LLR), liquidity (LIQ), return on assets (ROA), return on capital (ROE), net interest margin (NIM), non-performing loans (NPL) and leverage (LEV). The results indicate that LEV, LLR, ROE had a negative impact, ROA had a positive impact, and SIZE, DEP, LOA, LIQ, NIM, NPL did not significantly influence the CAR of Vietnamese commercial banks.