The list of firms includes financial heavyweights such as Credit Suisse Group AG, Morgan Stanley and UBS AG, which could face a three-notch cut in their long-term ratings. Other firms could suffer a two-notch drop, including Barclays, BNP Paribas, Citigroup, Credit Agricole, Deutsche Bank, Goldman Sachs Group, HSBC Holdings, JPMorgan Chase, Macquarie Group and Royal Bank of Canada.
Bank of America, Nomura Holdings, Royal Bank of Scotland Group and Societe Generale would see a one-notch dip.
"Capital markets are confronting evolving challenges, such as more fragile funding conditions, wider credit spreads, increased regulatory burdens and more difficult operating conditions," Moody's said.
The potential downgrades would not affect the markets, Lewis Van, a chief investment officer of Pride Investments Group, told Businessweek.
"This has been expected for quite some time," he said. "The banking industry -- including investment banks, retail banks and commercial banks -- will run their business more conservatively because of the increasingly tougher regulations."
The ratings agency also said 114 financial institutions in 16 countries across Europe would be placed under review.
The move follows Moody's downgrading of Italy, Malta, Portugal, Slovakia, Slovenia and Spain's sovereign debt rating, while putting Austria, Britain and France on a negative ratings watch. Those downgrades have a potential trickle-down effect on the nations' respective banks, which benefit from implicit government backing.
"While there are mitigating factors such as the currently supportive stance of many governments towards their banking systems and accommodative monetary policies, these are overshadowed by the aforementioned pressures," Moody's said. "Moody's expects that once the reviews announced today are resolved, its E.U. bank ratings will fully reflect the effects of currently foreseen adverse credit drivers."