Chinese banks saw their total assets rise 13.5 percent year on year to hit 141.34 trillion yuan (22.8 trillion U.S. dollars) at the end of June, the latest official data show.
The growth was the slowest since 2011, according to figures from the China Banking Regulatory Commission (CBRC).
Banks' liabilities reached 131.98 trillion yuan, up 13.2 percent year on year, the CBRC said on its website.
Smaller lenders, including joint-stock commercial banks and city commercial banks, posted annual growth of more than 22 percent for both assets and liabilities, more than double the expansion rate of large-sized lenders.
Big banks accounted for 43.3 percent of the banking industry's total assets and 43.2 percent of its total liabilities at the end of June.
Five banks were categorized as large-sized lenders in the CBRC's calculations -- Industrial and Commercial Bank of China, Agricultural Bank of China, Bank of China, China Construction Bank and Bank of Communications.