Despite struggles in its mortgage-related businesses, Fitch said Bear Stearns' solid franchises in global clearing and prime brokerage would keep its ratings stable.

Fitch said it expects liquidity and pricing challenges to prevail in the market over the next 18 months, leading to lower revenues and writedowns in the investment banking sector, but Bear Stearns should generate enough earnings to maintain capital and navigate through the cycle.

The ratings affirmation includes Bear Stearns' long-term issuer default and senior credit ratings at "A+" and its subordinated rating at "A." All three of those ratings are investment grade.

Bear Stearns had $62.1 billion in outstanding long-term debt as of Aug. 31, according to a note from Fitch.

Fitch also placed a stable outlook on Bear Stearns and its subsidiaries, meaning it is unlikely to upgrade or downgrade the company in the near future.

Shares of Bear Stearns fell $1.66 to $126.62 in afternoon trading.