Dean joins at Google's director of global policy and political campaigns.
She led Portland’s Brexit work and was at the agency for three years.
Prior to that she held several senior roles at the UK Foreign and Commonwealth Office (FCO).
She served as British High Commissioner to Barbados and the Eastern Caribbean for three years.
Previously, she served as the FCO’s deputy director of Europe and other senior roles, including head of strategic finance, head of comms to the EU and head of political team and the British Embassy in Washington DC.
Google confirmed Dean had joined its public policy team but would not provide further details of her role.