The mailer, created by agency 141 Worldwide, will drop just before Valentine's Day, and is being sent to the charity's entire database to encourage donations.
Fitting in with the Valentine's theme, the campaign highlights how the Dogs Trust aims to find a perfect match for every dog in its care, but that it needs additional funds too.
The pack contains a letter decorated with pink hearts. It is written from the perspective of Snowball, a Samoyed dog with a bad eye who has yet to find a home, with the line 'turn our lonely hearts into happy hearts'. A heart-themed leaflet with pictures of other dogs called Tizzy, Jim and Pete is also enclosed. The pack explains what specific levels of donations will go towards, for example medicine.