The pair will sit alongside the five existing partners, Laurence Green, Michael Wall, Robert Senior, Andy McLeod and Richard Flintham.
The managing partner, Green, said: "Five years on from our launch and we're as restless and ambitious as ever to develop our people, our brand and our business."
Wilsher replaced Chris Hirst as the agency's head of account management last May, following his departure to Grey Worldwide as managing director.
She was poached by Fallon in 2000 as an account manager and went on to run the Green & Black's, Starbucks and Umbro accounts as well as being part of the team handling the Sony Europe business, which the agency won from Saatchi & Saatchi in 2002.
Wilsher launched her career with BBDO's through-the-line agency McBains.
After two years, in 1998, she made the leap to Lowe Lintas as an account manager.
Crumpton relocated to Fallon from BMP DDB just two months after the agency's launch. She worked across the BT, Starbucks, BBC and Velvet accounts before ris-ing to the role of head of planning last year.
At BMP, she spent four years as a planner on Ministry of Sound, PG Tips and the Meat & Livestock Commission, among others.
Crumpton said: "It's hugely flattering and very exciting. But I like to think of it as more than a promotion of two individuals. It signifies an exciting step change for Fallon."