Mr Miliband will serve as business and energy secretary under his new party leader, who unveiled his top team on Monday.
Other new key appointments from Sir Keir, the new leader of the opposition, include making his former rival Rebecca Long-Bailey shadow education secretary.
Tottenham MP David Lammy was confirmed as the new shadow justice secretary on Monday afternoon, while Jonathan Ashworth remains as shadow health secretary.
Some of the bigger hitters from the Cobyn era such as John McDonnell, Diane Abbott, and Mr Corbyn himself have returned to the back benches.
But other allies of the former leader remain, with Cat Smith staying as shadow minister for young people and Andy McDonald taking over the shadow employment rights secretary brief.
Former housing minister John Healey has been moved to shadow defence secretary, while former shadow foreign secretary Emily Thornberry has been moved to shadow international trade secretary.
Meanwhile Jonathan Reynolds has been promoted to shadow work and pensions secretary, while Jo Stevens will lead for the opposition on digital, culture, media and sport.
Sir Keir has also found jobs for deputy leadership contenders Rosena Allin-Khan and Ian Murray, who will be shadow minister for mental health and shadow Scotland secretary respectively.
The new Labour leader announced his most senior appointments on Sunday, making Anneliese Dodds shadow chancellor and former leadership rival Lisa Nandy shadow foreign secretary.
Nick Thomas-Symonds is shadow home secretary and Rachel Reeves is shadowing Michael Gove as chancellor of the Duchy of Lancaster – effectively minister without portfolio.
With his role leading Labour’s BEIS operation, Mr Miliband is effectively reprising the role he held at the end of the last Labour government as energy and climate change secretary, a job that has since been renamed.
During Mr Corbyn’s leadership Mr Miliband remained on the backbenches, though he mostly held his peace and refrained from criticism, saying he did not want to be a “backseat driver”.
Clive Lewis and Jess Philips, both MPs who tilted at the party leadership but did not win enough nominations to get on the ballot, were notable by their absence from the shadow cabinet list. Barry Gardiner, an ally of Mr Corbyn who was at one point talked of as a contender, was also demoted from the frontbench.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies