He joins TNS Healthcare from WPP's Grey Healthcare UK, where he has worked since 2002 as managing director and European client services director.
David Hanlon, head of research, will support Duckham in leading UKI.
Duckham began his career over 20 years ago at Sharps/Dorlands/Zetlands Advertising. Since then he has worked with major global brands at a number of top agencies, including Geers Gross/Publicis, Adze Productions, FCB Bozell Worldwide, DC Interactive and LPB Advertising.
He also previously served as the European director of consumer communications for Bausch & Lomb.
Elaine Riddell, chief executive of TNS Healthcare, said: "With his creative vision, customer focus and true passion for branding, Mark was the ideal choice to help our clients build and maintain brand leadership in today's complex healthcare market.
"Mark brings a unique combination of research knowledge, 'big brand' expertise and healthcare insight to UKI, ensuring he can lead our team in creating the most powerful brand, communications and sales effectiveness solutions for our clients."