The broadcaster will now broadcast the BGT final at 19:30 BST on Saturday, when it was originally due to show the British Soap Awards.
A spokesman said ITV had "no desire to distract from the important cause" Grande's concert is raising money for.
ITV will instead broadcast the British Soap Awards on Tuesday at 20:00 BST.
Grande's One Love Manchester concert, which will be broadcast on BBC One, will raise money for those affected by the suicide bombing last Monday which left 22 people dead.
The gig, which takes place at the Emirates Old Trafford stadium, will feature Katy Perry, Coldplay, Miley Cyrus, Take That and Usher.
The Black Eyed Peas have also just been added to the line-up.
ITV said: "Ariana Grande's One Love Manchester benefit concert is bringing artists and the public together, and will raise funds for the Red Cross's Manchester Emergency Fund.
"We have no desire to distract from this important cause, so we have taken the decision to move the Britain's Got Talent Final from Sunday night."
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ITV has moved the final of Britain's Got Talent so it won't clash with Ariana Grande's benefit concert in Manchester on Sunday.