Moody’s has re-rated Nokia from A3 to Baa2, the second-lowest investment grade rating, and is keeping its outlook negative, it said.
It is the third agency to cut Nokia’s rating, after its rivals Fitch and Standard & Poor’s cut it last month.
"Visibility for Nokia's future operating metrics such as mobile phones sold or average selling prices is currently very low due to the transition in its product offering," Moody's said in a statement.
Last week Nokia reported a steep net loss for the past quarter to the end of June and lost its position as number one world smartphone maker to its rival Apple.
It is one of several technology companies struggling to manage the shifts in the market caused by products such as the iPhone and Google’s Android phones.
This week BlackBerry maker Research in Motion also said it would cut 2,000 of its employees globally – 11 per cent of its workforce – and slash its cost base as it struggles to produce a new model to revive its flagging sales.