The spring-themed mailpack was sent to existing donors at the end of April and focuses on an elderly dog called Sam.
The pack, created by agency 141 Worldwide, also covers the specialist care that such animals require and contains details of the Dogs Trust foster scheme.
Phil White, business director at 141 Worldwide London, said: "The mailer ensures supporters can visualise the dedicated treatment dogs receive from Dogs Trust and neatly illustrates what their donation will help pay for."
Dogs Trust is the UK's largest dog welfare charity and the eighth-largest charity direct mailer.
Late last year, the charity set up doggysnaps.com - a social networking site that is similar to MySpace - where dog owners can upload pictures, stories and profiles of their dogs.