Shayla Wiggins, 19, was looking for a water Pokemon (short for Pocket Monster) near Wind River in Wyoming, United States, on Friday (July 8). Instead, she found the body of a man floating in the river.
The teen told County 10 news that she woke up on Friday morning and started to play Pokemon Go - an augmented-reality game where users capture fictional "monsters" and train them to battle - on her iPhone.
She said she jumped over a fence to go towards the river as she wanted to get a Pokemon "from a natural water resource".
"I was walking towards the bridge along the shore when I saw something in the water," she said. "I had to take a second look, and I realised it was a body."
She called the police immediately, then led them to the scene.
The Fremont County Sheriff's Office has said that the death appears to be accidental, and there was no evidence of foul play. Investigators think the man drowned at the spot.
Speaking to CNN Money, Wiggins admitted that she "probably would have never went down there if it weren't for this game".
"But in a way, I'm thankful. I feel like I helped find his body. He could have been there for days," she said.
Pokemon Go's real-life problems
Pokemon Go, a free-to-play mobile game, was released on July 6 in the US, Australia, New Zealand and Japan. It isn't available in Singapore yet, with the developer saying that it will rollout the game in other countries soon.
Some robbers are also said to be using the game to lure victims to them.
Reuters reported that shares of Japan's Nintendo company surged after the release of its game. Nintendo shares were up over 20 per cent on Monday morning (July 11).
Pokemon Go has shot up to the top of the free-app rankings in Apple's US iTunes store, it said.