A spokeswoman for the charity confirmed that WWAV Rapp Collins Bristol pitched to retain the account but lost out to TDA.
TDA's brief covers strategic and creative direct marketing work as well as developing new products to promote the charity's Sponsor a Puppy programme and ways to improve the charity's legacy fundraising.
Trevor Hickman, direct marketing manager at the charity, said: "The Guide Dogs for the Blind Association has a loyal core of supporters. We want to grow this foundation of support while finding ways to identify and reach out to other audiences with new products so that the charity can continue its work.
"We spoke to various direct marketing agencies but TDA impressed us with their strategic insight and creative ideas. There is also a fantastic chemistry and cultural fit between our organisations."
Heather Westgate, TDA managing director added: "We are working in partnership with the charity to develop some exceptional ideas that will drive long-term growth by targeting whole new groups of supporters."
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .