He was also fined MYR210 million (US$49.4 million).
High Court judge Mohd Nazlan Mohd Ghazali also sentenced Najib to 10 years in prison for breach of trust and another 10 years for money laundering.
However, he ordered that all the sentences run concurrently. This means Najib will only serve a total of 12 years in jail.
Earlier the same day, the High Court found Najib guilty of all seven charges related to the misappropriation of RYM42 million of SRC International funds.
The 1MDB was formed by Najib Razak in 2009 for socio-economic development. Malaysian and US investigators held that the fund caused a loss of about $4.5 billion in the 2009-2015 period, while about $1 billion was sent to Najib’s personal bank accounts.