The agency won the account without a pitch. McCann Erickson, the incumbent on the account, won the Lloydspharmacy creative in November 2008.
Last month Lloydspharmacy's media account, previously handled by Universal McCann Birmingham, was awarded to Feather Brooksbank.
TDA will be responsible for strategic positioning as well as tactical campaigns that will launch in January. The appointment follows an existing relationship with TDA having worked with Lloydspharmacy on consultancy projects since February this year.
Work on the account will cover direct marketing, TV, radio, press and outdoor advertising. The agency will also be tasked with supporting online and local store activity together with employee engagement.
Lloydspharmacy director of marketing Claire Bayliss said: "The quality of the TDA team, their outstanding thinking about the future of our brand proposition, and the standard of work they’ve done for us already, have totally convinced us that they are the right partners.
"They fit perfectly with our desire for more integrated solutions, and we look forward to seeing how they deliver the creativity, engagement and impact we’re looking for."
Lloydspharmacy, which had a turnover of £1.8 billion in 2009, has more than 1,650 branches across the UK, based in community and health centre locations. It is a wholly owned subsidiary of the German pharmaceutical giant Celesio AG.