The appointment sees Mother become Orange's lead strategic agency as the company shifts its advertising strategy from running campaigns market-by-market to a more international approach.
The win is a vote of confidence in Mother, which had come under heavy criticism for its advertising for Orange in the UK.
Mother will act as a brand guardian with local agencies producing work using the strategic and creative framework developed by Mother.
The campaign will initially be launched in the UK, France and Switzerland in a test phase for the last quarter of the year. Orange is looking to roll the concept out to other markets next year.
"It is about trying to get one common campaign construct to run across key markets and Mother has come up with the overarching creative," Niamh Byrne, the head of PR and sponsorship for Orange UK, said.
"All the agencies will have to work together, you can't go from advertising in separate markets to one big global campaign just like that. We are putting together a campaign to reflect the increased commonality we are seeing across markets."
Byrne added that the appointment of Mother did not guarantee that the agency would take the lead for all of its multi-market advertising campaigns going forward.
The pitch was run by an internal global brand team, called OrangeWorld, overseen by the vice-president, worldwide brand, Alex Batchelor.