The expected announcement was made to Labour members at the party's annual conference in Liverpool on Saturday (24 September).
Corbyn won the election with 61.8% of the vote: a 2.3% higher share of the vote than when he beat Andy Burnham, Yvette Cooper and Liz Kendall in the 2015 election.
Corbyn's victory means his place at the top of Labour is secure for the time being, while former shadow ministers are presented with a dilemma.
A string of the top Labour MPs quit Corbyn's top team in protest over his EU referendum performance and Hilary Benn's sacking as shadow foreign secretary.
The mass resignations were followed by a vote of no confidence from Labour MPs, with just 40 backing the leader.
But a defiant Corbyn stayed on and has since promised to "wipe the slate clean" ahead today's announcement in a bid to unify the party.
Will some of the former shadow ministers return or decide to pursue their political objectives away from Corbyn and his allies?
Smith, who was little known outside of Westminster before the Labour leadership campaign, has already ruled out returning to the shadow cabinet. He also told IBTimes UK last week that there was not one big olive branch Corbyn could offer.
"I don' think there is one big gesture," he said. "I think he will have to work incredibly hard to rebuild the bridges that have been burnt over the last year, to try and illustrate to the Labour Party in parliament that he is serious about taking on the Tories."
The Pontypridd MP has faced a series of gaffes throughout the campaign. Smith notably suggested that the West should eventually negotiate with the self-styled terror group Islamic State (Isis), while he was forced to apologise for vowing to "smash" Theresa May "back on her heels".
Corbyn has also faced a number of setbacks, including the Virgin Train CCTV fiasco.
After the Labour leader claimed he failed to get a seat on one of the operator's services, Virgin then released footage of Corbyn apparently walking past a number of empty, reserved seats.
When Sky News' Darren McCaffrey later challenged him over the gaffe, Corbyn almost lost his temper and revealed he walked past the seats because he wanted to sit next to his wife.
"Yes, I did walk through the train. Yes, I did look for two empty seats together so I could sit down with my wife to talk to her. That wasn't possible," he said.
Corbyn's campaign also took a bizarre turn when he held a join press conference with reggae legends UB40. Corbyn thanked the group for their "incredible" endorsement, with just over a fortnight to go before the leadership election ballot closed.
Approximately 500,000 people voted in the latest Labour leadership contest – a turnout of 77.6%. The 2015 contest saw 422,871 votes with a 76.3% turnout.
The latest opinion poll from YouGov for The Times, meanwhile, put the Conservatives nine points ahead of Labour. The survey, of more than 3,200 voters between 19-21 September, put the Tories on 39% and Labour on 30%.