The agency pitched against undisclosed GSK roster agencies to secure the business. It is tasked with developing acquisition and retention activity across online and offline platforms to help grow Sensodyne's market share.
This is the second piece of toothcare business that Joshua has won from GSK since it was appointed to its £25 million healthcare and nutrition roster last year after a review.
Earlier this year, the agency won the £5 million Aquafresh account.
Sensodyne's below-the-line work will need to integrate with its above-the-line strategy, which is handled by Joshua's WPP sister agency Grey.
Media is with MediaCom, also a WPP company.
A Sensodyne spokesman said: "Using DM is a fundamental part of our long-term plans. Joshua provided a very strong integrated, strategic, data-driven response, which we are confident will help develop our business and support our TV investment."