The former Westlife star - who has two children, nine-year-old Molly and Lilly-Sue, eight, with ex-wife Kerry Katona - proposed to the Australian singer-and-actress almost four years ago but the pair never set a wedding date and their spokesperson has confirmed they have "mutually" called time on their six-and-a-half year relationship.
A statement released by their publicist said: "DeltaGoodrem and BrianMcFadden regretfully announce that they are no longer engaged, and after much consideration, have mutually decided to end their relationship.
"This decision has been made with a lot of soul searching from both parties with the realisation that they have grown apart. They leave the partnership with respect for one and other, wishing each other success and happiness for the future.
"Delta and Brian appreciate there will be interest regarding this announcement but request that their time together is respected and they are given privacy during this time of transition."
Brian later took to his twitter page to praise Delta for giving him "the best years" of his life.
He wrote: "i love delta and always will. She is one of gods living angels. I thank her for giving me the best years of my life. Please give us time x (sic)
The pair have been spending increasing amounts of time apart lately with Brian, 30, remaining in his adopted home of Australia where he is a judge on TV show `Australia`s Got Talent` and 26-year-old Delta recording her fourth album in Los Angeles.