Shares in Bankia, the Spanish lender forged from the merger of seven savings banks, fell 1.9 percent to 3.68 euros when trading began for the first time on Wednesday.
The government has pushed Bankia and smaller rival Banca Civica to list their shares to shore up capital after the collapse of a property boom in 2008 left lenders heavily exposed to bad debts.
The stock market flotation is seen as a key test of Madrid's strategy to strengthen Spanish banks and markets will be watching closely to see how the shares perform.
Bankia, which is run by former IMF chief and Spanish economy minister Rodrigo Rato, priced its shares at 3.75 euros, a 60-percent discount to book value, to attract shareholders amid market tensions over the European sovereign debt crisis.
It originally planned to sell shares at 4.41 euros to 5.05 euros.
Banca Civica, which was forged from the merger of four savings banks, set the price for its stock market debut on Thursday at 2.70 euros, the bottom of the marketed range and also a discount of around 60 percent to book value.
Both Bankia and Banca Civica passed the stress tests published on Friday by the European Banking Authority to see if they can survive a theoretical slide in stock, bond and property prices during a two-year recession.
But they only just achieved the bare minimum requirement of rock solid core Tier One capital ratio of 5.0 percent of total assets.
Five Spanish banks were among the eight European lenders which failed the stress tests.