The badly-burned body of Lauren Patterson, 24, from West Malling, was found in the desert in October 2013.
She had been working at the Newton British School in the capital Doha and disappeared after a night out.
Badr Hashim Khamis Abdallah Al-Jabr was found guilty of stabbing her. However, the conviction was later quashed and a retrial ordered. It ended on Sunday.
His accomplice Muhammad Abdullah Hassan Abdul Aziz was jailed for three years.
Ms Patterson's mother, Alison, had travelled to Qatar on several occasions to fight for justice for her daughter.
She was in court when the conviction was upheld and told BBC South East she was "very relieved".
The verdict was handed down after the judge asked Mrs Patterson what judgement she wanted.
"I told the judge I did not want to forgive," she said.
Al-Jabr now has 60 days in which to launch an appeal.
The death sentence for a man who murdered a Kent teacher in Qatar has been upheld following a retrial.