MacDougall said in a letter to colleagues and contacts Wednesday he is leaving the post and taking a new job in London, England, with a strategic communications firm. He will leave Harper's office after the prime minister attends the G20 meeting in Russia in the first week of September.
MacDougall, who started in the Prime Minister's Office as a press secretary in 2008 and was named director of communications in the spring of 2012, said in the note that his desire to live and work in London is a long-standing one.
He will be a senior executive consultant with MSLGROUP Publicis Groupe's London office beginning in November, the firm said on its website.
"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," Jeremy Sice, CEO of MSLGROUP in the UK, said.
MacDougall thanked his colleagues "past and present for showing me the ropes, sharing your knowledge, and imparting your wisdom." He also thanked MPs and wished them continued success.
"Most of all, I am grateful for the prime minister's confidence. It has been a rare privilege to watch firsthand how the prime minister has led Canada through these tough economic times. To have been a small part of this endeavour will forever rank as one of my proudest accomplishments," MacDougall said.