Budimlija will be responsible for developing a strategic planning function across the Grey Global Group-owned agency, which boasts a client list including Mars, Coca-Cola and the Post Office.
She joins from Nitro London, where she has been head of planning for the last 12 months; before which she worked on campaigns for Transport for London at M&C Saatchi.
Nick Spindler, chief executive at Joshua, said: "Joshua G2 is a kind of multi-disciplined nirvana for anyone who wants to craft client solutions with no restrictions in this new media neutral world. I think she's going to have great fun working with us."