Johnston, who also joins as executive vice president for the group, will be responsible for Aeroplan's operations in Europe, including Nectar, taking up the position in January.
Johnston will also oversee operations of Rewards Management Middle East, the operator of Air Miles programs in the United Arab Emirates, Qatar and Bahrain.
Joining from Pepsico International, Johnston most recently held the position of general manager, Quaker Tropicana, UK, and previously vice president beverages marketing for Europe.
Last week Groupe Aeroplan acquired Carlson Marketing for $107m. Johnston's role however excludes leadership responsibility over the agency.
Johnston will also be responsible for LMG Insight & Communication, a customer-driven insight and data analytics business.