Presiding Judge Abd Allah al-Saadi told the court on Thursday that the earlier verdict was upheld. The verdict sentenced Anatoly Bilashkov and Vassily Pokchov to jail for life for the 13 February killing of Salim Khan Yandarbiyev, a former Chechen president who lived in exile in Doha.
A life sentence in Qatar is 25 years. The decision is final, although defence lawyer Muhsan Dhiab al-Suwaidi said he would use all legal channels to challenge the ruling.
Judge Ibrahim Salah al-Nisf last month said the court had been lenient in not sentencing the pair to death, as the prosecution had sought, and accused the "Russian leadership" of ordering the killing.
Moscow has insisted the two are innocent.
The killing of Yandarbiyev, who was briefly president of separatist Chechnya during its war with Russia, threatened a diplomatic breach between the Gulf state and Russia.
Itar-Tass news agency reported that, as the appeal had
failed, only intervention by Qatari ruler Shaikh Hamad bin
Khalifa al-Thani could free the men.