Freuds' associate board director Adrian Warr will join Portland later this month as an associate partner.
Cohn & Wolfe account director Caroline Edgar has also been recruited as a consultant in the corporate division.
Portland was founded by Tim Allan in 2001 as a public affairs specialist. It is now seeking to beef up its 12-strong comms division in the UK, where clients include Coca-Cola GB, Google and AB InBev.
The agency moved up 13 places to 30th position in PRWeek's 2011 Top 150 PR Consultancies table.