'PN will help us articulate the strength of our business to our stakeholders and align our PR strategy across Europe,' said Yahoo! Europe director of corporate comms David Sawday.
Cohn & Wolfe maintains accounts for trade PR and dating spin-off Yahoo! Personals. Text 100 did international comms until February.
Yahoo! said PN's account was designed to closer align comms in Europe and the US. It represents Yahoo!'s first global PA brief.
The company is continuing to fall behind its younger rival Google in the search-engine stakes – a survey this week revealed only 7.5 per cent of online searches in the UK were conducted on Yahoo!, with Google accounting for nearly 75 per cent.
The Hitwise poll also suggested Yahoo! was behind Microsoft's MSN, which scored 7.8 per cent.
But like its rivals, Yahoo! has branched out from a simple search engine to offer news services, a web directory and email.
Yahoo! courted controversy last year when it agreed to censor search engine results in China, a decision also taken by Google and Microsoft. Free-speech advocates have lambasted the firms for their implied 'collaboration' with an oppressive regime.
Yahoo! defends its position but is constantly under attack. Last week a troupe from free-speech advocacy group Reporters Without Borders went to the firm's US HQ demanding a meeting with executives. Yahoo! later agreed to meet the protesters.
PN UK director Jonathan Hemus heads the UK arm of the account, reporting to Sawday.