Devon and Somerset Fire and Rescue Service recounted the incident on their Twitter account, saying it happened Tuesday near Exeter in England.
Rescuers were trying to speak with a young woman who they said "was thinking of taking her own life on a bridge" over a highway.
Multiple agencies and negotiators were on the scene, but officials said the situation was becoming more dire.
That's when one of the fire crews had the idea to bring along Digby, their "defusing" dog.
"Digby helps crews who have been exposed to trauma during talking therapy 'diffusing sessions," they explained.
"When Digby arrived, the young woman immediately swung her head round to look, and smiled," they said.
Rescuers said that began a conversation about Digby and his role with the fire service.
"She was asked if she would like to come and meet Digby if she came back over the railings, which we are pleased to say she did," they wrote.
Digby's story and happy ending for the woman quickly resonated with people online. The tweets soon went viral, garnering more than 63,000 likes in less than 24 hours.
Thousands of dog lovers praised Digby for a job well done, calling him a hero.
If you or a loved one is feeling distressed, call the National Suicide Prevention Lifeline. The crisis center provides free and confidential emotional support 24 hours a day, 7 days a week to civilians and veterans. Call the National Suicide Prevention Lifeline at 1-800-273-8255. Or text HOME to 741-741 (Crisis Text Line)