Bushell, who took on the role nine months ago following Mash Media's acquisition of International Confex from UBM, has moved on to new challenges.
Agostini, wife of owner and Mash Media MD Julian Agostini, will take on the role from June, heading up International Confex and the Event Production Show, which will co-locate in 2015.
Bushell said: "I am extremely proud to have helped put Confex firmly back on the map and led the effort to give the show a solid platform to take it forwards at Olympia London in 2015. I wish the new team well and know the show is in very capable hands."
Agostini said: "I am looking forward to ramping up to the next level with this great team behind me and returning Confex to its position alongside IMEX and EIBTM as a must-attend in the international MICE calendar."