Frazer, who joined Imagination in 2010, was formerly vice president of Maritz Europa and then deputy chairman at Grass Roots Eventcom.
Douglas Broadley, CEO of Imagination EMEA, said: "We thank Graham for his commitment to Imagination. Our world class team will continue to offer our clients the very best global creative travel and logistics service and we have agreed with Graham to retain a working relationship with him on key client projects."
Frazer added: "At the age of 67 and after 40 marvellous years in this industry the time has now come for me to take life easier.
"I have thoroughly enjoyed my career with Travel Awards, Maritz Travel, Grass Roots and now finally Imagination. Having done so many extraordinary things in so many wonderful places I cannot imagine a more interesting and rewarding working life.
"I leave Imagination in safe hands with an established and experienced global travel and logistics team and
look forward to working with them in the future on high profile client projects."
Imagination recently retained its Jaguar Land Rover account.