The move follows the recent appointment of Dave Scott as Psion's new global communications director.
Fishburn Hedges will work alongside Psion's new management team to raise the firm's profile across key business and trade media in the UK and Europe-wide. The agency is also charged with working alongside Psion's overseas agencies to provide a consistent corporate story in different markets and will develop a campaign highlighting the firm's product range.
Scott said: 'We've been relatively quiet in the past few years, but there is a massive heritage of innovation at Psion. We want to make a once iconic brand great again and, with a strong new management team in place, there's a great story to be told.'
The Fishburn Hedges team is led by chief executive Simon Matthews.
The appointment does not impact the role of Brunswick, which remains Psion's City and financial PR agency.