Dog handler Constable Regan Turner said he was tracking an alleged offender through rural property when he deployed Kosmo.
"I knew when I got to the area and couldn't find him that something had happened. He doesn't run away from me. I knew he was lying somewhere, it was just a matter of getting to him," he says.
It took 20-25 minutes to eventually locate Kosmo and administer first aid.
"Kosmo had lost a lot of blood, I thought he was a gonner," Constable Turner said.
"The cut was to his jugular — he's very lucky to be alive.
"Kosmo's saved me on a few occasions and I can't thank him enough for what he did last night. It was either him or me, unfortunately."
A 29-year-old man from Christchurch was arrested at the scene and is due to appear in Christchurch District Court today on various charges.
Kosmo and Constable Turner feature in the current season of Dog Squad.