Piraeus, which is Greece’s fourth-largest bank, is to raise just over one billion euros by selling shares and bonds.
Like other Greek banks, Piraeus has been hurt by the country’s debt crisis.
It is raising cash to be better placed to deal with the recession and satisfy stricter rules on the amount of capital banks must hold.
It also wants to reduce its dependence on the European Central Bank for funding.
Piraeus is the second Greek bank to opt for a big capital boost to strengthen its balance sheet.
National Bank, Greece’s biggest lender, raised 1.8 billion euros earlier in October, boosting its capital adequacy ratios.