MacDougall, who has worked for PM Stephen Harper in the role since April 2012, will leave his job next month.
Starting as senior executive consultant for the agency in November, he will report to MSLGroup UK CEO Jeremy Sice.
‘Andrew’s unique combination of political communication, crisis communication, and digital media experience will bring a fresh perspective to our clients as they navigate an increasingly complex communications environment,’ said Sice.
MacDougall first joined the PM’s Office as deputy press secretary in 2008, and before this worked at Hill+Knowlton Strategies in Canada having been a freelance journalist.
Harper's seventh director of comms in seven years, he also led the PM's digital and social media teams.
It is reported that he announced the departure in a letter to staff early Wednesday morning.