By Patricia Kowsmann

LISBON--Banco Comercial Portugues SA (BCP.LB), Portugal's largest bank by market capitalization, was among the 25 eurozone banks that failed the European Central Bank's financial-health check, although it has already taken enough measures this year to shore up its balance sheet.

Three Portuguese lenders--Banco Comercial Portugues, Banco BPI SA (BPI.LB) and state-owned Caixa Geral de Depositos SA--were tested by the ECB, which reviewed the financial status of 130 banks before it takes over their supervision in November. Novo Banco, that resulted from the break-up of the collapsed Banco Espirito Santo SA in August, wasn't submitted to the test.

While Banco Comercial Portugues showed its core capital buffer will stay above 8% of risk-weighted assets under a basic-case scenario where the economy develops as expected until 2016, it failed to maintain a capital buffer of at least 5.5% if the European Union slips into a two-year recession and Portugal slips into a three-year economic contraction.

The test was based on bank data for the end of 2013, however, and the Portuguese lender said it has already taken steps in 2014 to boost its capital and, therefore, its ability to absorb losses.

In July, it raised 2.24 billion euros ($2.8 billion) in a rights issue, allowing it to pay a chunk of the EUR3 billion in state aid it received in 2012. The lender has €750 million left in state money which it said it will repay by 2016. It has also committed to selling assets and cut costs.

Patricia Kowsmann at patricia.kowsmann@wsj.com