Shearman, currently the international planning director at TBWA\Worldwide, will take the title of global planning director. He will work alongside JWT's executive creative director Nick Bell, and will report to the director of strategy, Marco Rimini.
Rimini said: "One of the great things about a new client is the opportunities it offers to recruit new talent. HSBC is a unique opportunity and Paul is that unique talent."
Shearman, the planner behind the recent campaign for John Smith's starring the comedian Peter Kay, joined TBWA in 2000 following a three-year spell at BMP DDB, where he was a senior account planner on the Sony Europe account.
The New Zealander was part of the team that guided Sony to victory in the long-term advertising effectiveness category at the European Association of Advertising Awards in 1999.
He launched his career at Leo Burnett in Auckland and also worked for Chiat/Day/Mojo and Bates before moving to the UK in 1997.
Shearman said: "I am very excited to be joining both J. Walter Thompson and the HSBC team. Both are highly respected and successful global brands and this role offers the opportunity to work as part of a genuinely integrated communications team with a client that believes in the power of great ideas and great ads."
JWT succeeded Lowe as the lead agency for HSBC in May after WPP saw off challenges from Publicis Groupe, Interpublic and Omnicom. The entire account is co-ordinated by Toby Hoare.