KUALA LUMPUR—Former Prime Minister Najib Razak is due to face prison after Malaysia’s highest court dismissed his final appeal of corruption convictions related to his role in one of the world’s largest financial scandals.

Mr. Najib, 69 years old, was sentenced to 12 years in prison in 2020 after being convicted of seven charges including abuse of power, money laundering and criminal breach of trust, and fined almost $50 million. His punishment was stayed while he appealed the verdicts, all of which were upheld by Malaysia’s Federal Court on Tuesday.

Mr. Najib served as prime minister of the Southeast Asian nation for almost a decade until he lost a 2018 election amid outrage over the scandal involving state investment fund 1Malaysia Development Bhd., known as 1MDB. He continued to serve in Parliament after losing the election.

Mr. Najib, who has denied wrongdoing, faces dozens of other criminal charges that are still before the courts.

Write to Feliz Solomon at feliz.solomon@wsj.com and Ying Xian Wong at yingxian.wong@wsj.com