In a brief statement issued by Goodrem's publicist, the star couple said they had been hoping to keep the news private.
However, following reports that the 23-year-old had refused McFadden's marriage proposal, they decided to set the record straight.
"Contrary to false reports, the couple were hoping to keep the news private however they feel it is important to now confirm their exciting news," the statement said.
Goodrem began dating Irish singer McFadden in 2004, shortly after ending her nine-month romance with Australian tennis player Mark Philippoussis.
Their relationship was the focus of intense tabloid media scrutiny in the UK after it was alleged Goodrem was responsible for McFadden, a father of two, ending his then-marriage to ex-Atomic Kitten Kerry Katona.
"It was a really awful time," Goodrem told ABC TV's Andrew Denton in August.
"That was like the pinnacle of when I started to go, 'this is not enjoyable anymore. This is really not fun'.
"And I felt really betrayed ... I felt that it was unjustified - the comments being made."
No wedding date has been set. © 2007 Australian Broadcasting Corporation