InboxDMG will initially develop a new creative look and feel for the website, which will incorporate content from some of PDSA's external microsites.
and InboxDMG will work closely with design agency cxpartners to refine the site's architecture and navigational structure.
The goal for this first phase of the redesign is to better meet the needs of the organisation and users and raise awareness and income by attracting new audiences.
Oli Christie, InboxDMG's creative director, said: "InboxDMG will be working with PDSA to develop a new modern look and feel for the website, updating its architecture around core needs - audiences, key tasks, business and marketing, technology, improving usability and accessibility to help users find what they're looking for, and providing a flexible platform for future campaigns and growth."
PDSA's in-house web development team will work on the rebuild and re-programming of the website.
Helen Jeffs, web manager at PDSA, said, "With digital now central to our fundraising and revenue generation efforts, it's vital that we get the look, feel and functionality of the website right to allow us to engage with, and meet the needs of, our supporters online.
"Once we've accomplished that we'll focus on further developing the site to help us meet our income generation objectives."