Debra Suierveld and her family assumed their dog Abby had died after she ran away in 2008 from their home in Apollo, Pennsylvania.
But decade-old sadness turned to joy on Saturday when Suierveld received word someone had found the dog, reports news.com.au.
The black Labrador mix showed up on George Speiring's front porch in Lower Burrell, 16km west of Apollo.
Speiring contacted Animal Protectors of Allegheny Valley, which discovered the dog's microchip and was able to contact Suierveld.
Someone had taken good care of Abby over the years. Abby is in great health and remembers things the family taught her, Suierveld said.
"She would lie on the floor and cross her paws, and she remembers my daughter's commands, and she remembers the commands I taught her," Suierveld told KDKA-TV.
Suierveld called her 22-year-old daughter, who is a student at Miami University, in Oxford, Ohio, to share the news.
"She cried," Suierveld told the Tribune-Review.
"I didn't even know what to say," Suierveld said.
"I was like, 'Oh my goodness.' She kind of came back from the dead.
"We mourned you Abby."
Suierveld's family has planned a reunion dinner on Sunday to welcome Abby back.
Debra joked the family believed Abby was hiding out in the witness protection program.
She said if Abby could talk she would have quite a story to tell.
Abby was last seen by the family playing in the backyard near the woods in the Suierveld backyard with their children. She was later spotted about 14km from the house but then nothing, until now.
"We thought she had passed away,"
"It feels like a part of my kids' childhood is back, part of our family is back," Suierveld said. "It's pretty awesome."
It is not known where Abby has been all this time.