He had been tipped to win another term in office easily last year and extend his coalition's six-decade stranglehold on power, only to be soundly defeated by his former boss, Mahathir Mohamad, who rode a wave of public anger to the premiership.
In the months that followed, once-dormant investigations into 1MDB were relaunched and Najib was hit with dozens of corruption charges linked to the scandal.
In Wednesday's trial, Najib will face seven charges of corruption and money laundering over the alleged theft of some 42 million ringgit (USD10.3 million) from SRC International, a former 1MDB unit.
It is only a fraction of the money allegedly stolen from 1MDB, and hundreds of millions of dollars are believed to have ended up in Najib's accounts alone.
He has denied any wrongdoing.
Najib was initially due to stand trial in February, but appeals by his defence team over procedural matters saw his case put on hold until a judge last week ruled the trial should finally proceed.
While many of his cohorts have been caught and charged in Malaysian courts, the alleged mastermind behind the 1MDB scandal, playboy financier Jho Low, is still at large.
Local media reported the former premier made a bid on Monday to delay his trial yet again, although this appeared to have failed.
Cynthia Gabriel, head of the non-profit group The Centre to Combat Corruption and Cronyism, told AFP that Malaysians had been waiting "too long" for the trial to begin.
"The multiple delays are so obvious and deliberate, it's a way of pushing the trials further," she said.
"It's apparent that the former ousted PM, isn't quite ready to sit in the dock and face trial, be cross-examined, and get embarrassed." Najib's former mentor turned nemesis Mahathir, now 93 and in his second stint in office, has pledged to bring him to justice and bring back the huge sums of cash stolen from 1MDB.
The US Department of Justice, which is investigating the controversy as money was allegedly laundered through the US financial system, believes USD4.5 billion in total was looted from 1MDB.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)