Edelman's managment consultancy arm First&42nd already handles CSR work for Orange, an account headed by director Jane Atkin, who will assume responsibility for the wider B2B brief.
Edelman replaces incumbent Cohn & Wolfe on the Orange account. While losing the B2B work, C&W has been re-appointed for Orange's consumer PR business in the UK and internationally.
Budgets are still being confirmed, but industry speculation suggests Orange's consumer and B2B accounts are worth up to £1m.
Edelman and C&W report to Orange group director of corporate affairs Denise Lewis, who also co-headed the pitch process.
Meanwhile, Brunswick partner Locksley Ryan is to join Edelman, to develop the independent global PR network's European corporate offering and to help expand First&42nd.
Reporting to Edelman international president Alison Canning, Ryan becomes head of Edelman's European corporate practice - a newly created role - and chairman of First&42nd.
His appointment on 19 August coincides with the promotion of First&42nd CSR head Liz Freeborn to UK managing director.
Freeborn and Ryan effectively replace former First&42nd European MD James Thellusson, who was promoted to Edelman UK chief executive last month (PRWeek, 5 July).
On Ryan's role, Canning said: 'The majority of Locksley's work will be on business development and client work, but we also want him to help us recruit and strengthen products.'
She added Ryan will look to bolster the corporate practice and double its current headcount of 50 in two years' time: 'Our focus is going to be on moving into C-suite (CEO, CFO and COO) services and combining that with a financial capability.'