Najib was jailed last year after Malaysia’s Federal Court upheld a guilty verdict and 12-year prison sentence handed down to him by a lower court.
Najib, 69, claimed he had not received a fair hearing, alleging one judge had a conflict of interest and that his new legal team was not allowed enough time to study the case documents.
But the Federal Court on Friday dismissed the challenge.
“There has been no prejudice and no failure of justice,” Judge Vernon Ong said.
The former prime minister can no longer challenge the conviction in court but he has applied for a royal pardon which, if successful, could see him released without serving the full 12-year term.
Investigators have said some $4.5bn was stolen from 1Malaysia Development Berhad (1MDB) – co-founded by Najib during his first year as prime minister in 2009 – and that more than $1bn went to accounts linked to Najib, Al Jazeera reported.
Najib was charged after he lost a general election in 2018. He was found guilty by a high court in 2020 of criminal breach of trust, abuse of power and money laundering for illegally receiving about $10 million from SRC International, a former unit of 1MDB. He lost all his appeals.