Walker, who joined Fallon more than three years ago, is scheduled to start his new role as the creative leader of Publicis Mojo's Sydney office in September.
Walker said: "There were a lot of personal decisions involved, but professionally it's an opportunity for me to assume a little bit more responsibility and to do better work, and I think that's always really exciting. Fallon is such a difficult place to leave, I've really enjoyed my time here, but I think it's sometimes just good to have a change."
Wilson, who has been a senior copywriter at Mother for the past four years, will join Mojo's Melbourne office as the creative director. He will partner Christy Peacock.
Darren Spiller, the regional creative director at Mojo, said: "I am all for hiring Australians, but I didn't find anyone here who suited the roles."
This is not the first time that Mojo has boosted its creative offering with British talent.
In September 2003, the agency poached Nick Worthington, the former creative director at Abbott Mead Vickers BBDO and partner to Paul Brazier, to join its Auckland office as the executive creative director.