The social networking site, used by more than nine million members in the UK, will continue to work with Edelman on a European and global basis.
The appointment follows a pitch process revealed by PRWeek.
The site recently hit the headlines when a massive data breach saw a file containing 6.5 million passwords posted online. The company took to fellow social media network Twitter to update both the press and consumers.
Lansons has formerly worked on LinkedIn's account, at which time it worked on corporate, consumer, trade, digital and public affairs.
The site has in excess of 161 million members in more than 200 countries.
LinkedIn’s agency switch comes as Twitter nears the end of its hunt for its first UK PR agency. The social network is seeking a consumer agency to position it as a people-focused brand and challenge Facebook.