'Thinking Out Loud' singer Ed will now headline on Friday 28 August in replacement of Canadian star Justin, who had to pull out due to "unforeseen issues".
Ed will be performing a full 90 minute set at the music festival.
Ed, who performed on three consecutive nights at Wembley Stadium last month, said: "I'm delighted to be playing Fusion Festival after stepping in at the last minute to help out the guys at Fusion and support The Princes Trust. Birmingham crowds are always lively, so I can't wait to come back. See you in a few weeks!"
Rudimental will headline on Saturday, while McBusted will headline on Sunday night. Other acts performing across the weekend include Ella Henderson, Labrinth, Union J, dappy, Fuse ODG and Jess Glynne.
Damien Sanders, event director for Fusion, said: "This is incredible news. When Ed heard that Justin Bieber had pulled out he contacted us and offered to step in at the last minute, this is an amazing gesture from an all-round great guy and Ed really has saved the day, we are all eternally grateful.
"We look forward to a spectacular show and are delighted to have secured one of the biggest acts in the world."
Justin's now-cancelled headline gig at Fusion was set to be his first appearance in the UK since his 'Believe Tour' in 2013.
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