Kris Faafoi will take over Corrections, and Shane Jones, if cleared by the Auditor General, will get regional development, forestry and associate finance.
"He is a talented politician with an important contribution to make," said Mr Shearer about Mr Jones.
Mr Shearer said his decisions were based on choosing the best person for each job.
"My shadow Cabinet includes a mix of new talent and experienced hands. They are raring to go and keen to get stuck into tackling the issues that matter most to Kiwis."
Amongst other promotions, first-term Dunedin North MP David Clark leaps to number12 in Labour's rankings and takes on economic development, while former party president Andrew Little will take over the justice role from the departing Charles Chauvel and will also take on tourism. Sue Moroney will take on Mr Little's current ACC portfolio. Former leader Phil Goff keeps his foreign affairs role, but adds state services.
Two other long-serving Labour MPs - Lianne Dalziel and Trevor Mallard - have been moved out of the top 20 into the unranked portion of the caucus - Labour only ranks its top 20 MPs by number. Mr Mallard has been allocated the Internal Affairs portfolio.
Mr Shearer said although Mr Mallard and Ms Dalziel had been moved out of the Shadow Cabinet, they would retain significant roles and had recognised the need for rejuvenation.