The hires follow the departure of David Prideaux, the executive creative director, who was in the role for four years.
Prideaux was in charge of the creative department at Publicis Dialog for four years before its 2011 merger with Chemistry.
Fletcher and Iles will join in the autumn as group creative directors, reporting to Emma Rush, who was promoted to managing director at the end of July.
They will take the creative lead across Publicis Chemistry’s clients, including Royal Mail, EE, Gü and Gatwick Airport, as well as work on some Publicis UK accounts.
At TBWA, Fletcher and Iles handled clients including Nissan, Four Seasons, Game and SCA’s Tena. Their work spanned above-the-line, digital, eCRM, social and retail channels.
They created Harrods’ first Christmas campaign last year and recently led TBWA’s winning pitch for Royal Caribbean International.
Before TBWA, Fletcher and Iles were board directors and creative directors at Golley Slater. They also led – and won – pitches for COI and Royal Mail while at Proximity London.
Rush said: "Marcus and Jason have been on Publicis UK’s radar for a while now. Their diverse creative experience, skills and awards bring a unique dynamic to Publicis Chemistry and Publicis UK for many of our integrated clients. They will also play a key role in Publicis Chemistry’s management team."