"We will always love you, Pooka Diamanté Jefferson," the star wrote.
The collection includes everything from country-themed pet apparel to music-inspired toys you can treat your pet to.
"It hurts so bad to say goodbye to these sweet companions but their love is always worth it.," Lambert writes in a social media post.
The pop star captioned the sweet snapshot with a Katy Perry lyric.
Proceeds from "Da Ruba Girl" will benefit Stray Rescue of St. Louis.
The products include hoodies, toys, bowls, leashes and more.