Pragya Thapa, 15, from Sunsari district in east Nepal, hanged herself after watching Brazil, who were her favourite team, suffer the surprisingly one-sided defeat.
Nepalese police officer Sharad Thapa said: "She was anxious to see Brazil in the final, but it went down to Germany.
"Some of her friends started teasing her for supporting Brazil. Later in the morning, she took an extreme measure by hanging herself in her own room."
Pragya lived in a remote village around 250 miles from Nepal's capital city Kathmandu.
Her mother found her hanging from the ceiling in her room. She was living with her mother and grandparents while her father was abroad working.
Her body has been sent for an autopsy.