Newspapers reported the accident happened when Lim Vanthan, 17, and his family were planting rice at the weekend near their home in Phnom Penh.
Vanthan decided to go for a swim and during his dip caught a prized 20cm fish with his hands.
But the high school student's excitement was short-lived when his catch squirmed away and jumped into his mouth, where it became stuck because of barbs running down its back.
The teenager died of suffocation before he could receive treatment at a clinic, newspapers said.
"This is an accident, but it shows we must all be careful," concluded the Rasmei Kampuchea (Light of Cambodia) newspaper.
"Accidents can happen at any time."