Short and Sweet (But Heartfelt):

“I’m so sorry to hear about [dog’s name]. They were such a good dog and so lucky to have you. Sending you all my love.”

A Little More Personal:

"I know how deeply you loved [dog's name]—and how much they loved you. That kind of bond is forever. Please know I’m thinking of you."

If You Knew the Dog Well Too:

“I’ll miss [dog’s name] so much. They brought so much joy and personality into every room—and every walk. I’ll never forget [a favorite memory]. I know this loss is so heavy. Sending a big hug your way.”

Gentle and Spiritual (if that fits):

“I believe [dog’s name] is running free and happy now, waiting for you across the rainbow bridge. But I know your heart must ache right now. I’m so sorry you’re going through this.”

If You’re Not Super Close But Want to Reach Out:

“I just heard about [dog’s name], and I wanted to say I’m so sorry. Losing a dog is losing family. Thinking of you during this difficult time.”