Mathews, who was previously head of research, will manage the company's London-based head office.
Since joining Kadence in 2004, Mathews has restructured and repositioned the firm's insight business and helped build its client base.
Simon Everard, Kadence group chairman, said: "Kieron has played a key role in the company's development over the past five years and his new position is fully deserved.
"This is the perfect time to strengthen our UK management team and it will enable me as group chairman to focus on growing the business globally from our offices in the US, India and Asia-Pacific."
Kadence, which was founded in 1992, has offices in Boston, London, Delhi, Kuala Lumpur, Singapore, Jakarta and Hong Kong. Its clients include CNBC, Canon, Hitachi, Nestle and Novartis.
Mathews said: "This is both an exciting and challenging time to manage the European team which continues to see strong demand for its business insight and fieldwork services.
"I believe that stretched budgets are encouraging research buyers to look beyond the largest agencies for teams that are more flexible, offering greater value and delivering the kind of specialist knowledge that will help them reach and extract insights from their target markets."