JWT has a long-standing relationship with its owner, Mondelez International, and worked on Philadelphia for decades until 2013, when the brand called a pitch that was won by Bartle Bogle Hegarty.
But the relationship lasted only a year and one campaign. BBH and Philadelphia parted ways in 2014 and it was initially reported that the business was moving in-house.
Philadelphia spends about £7 million on media in the UK. Other key markets include France, Germany, Italy and the Middle East, which is included in JWT’s remit.
Greta Hammel, Philadelphia's European equitymManager said: "We are delighted to re-appoint JWT and look forward to working closely with a tried and tested partner who shares our passion and vision. This new chapter for Philadelphia across Europe will create exciting new creative work to drive a great brand further forward still."