The Labour prime minster, who led the UK between 2007 and 2010, has agreed to be part of an advisory group from outside Wales.
It will advise ministers on how services such as schools, transport and the NHS could operate once the lockdown restrictions have eased.
But the Tories said Mr Brown was the "last thing that people in Wales need".
Counsel General Jeremy Miles has been tasked with leading the recovery.
He will also help plan for Wales' post-pandemic future.
First Minister Mark Drakeford said it was "the biggest challenge" the devolved government has faced.
The Welsh Government said he will not be paid.
Full membership of the advisory group is still being finalised, though other members include Paul Johnson, director of the Institute for Fiscal Studies, and Dr Rebecca Heaton, of the UK Committee on Climate Change.Mr Miles is expected to give more details about the panel in a press conference on Wednesday.
The Welsh Government confirmed the former prime minister had offered his services for free, with his first session likely to be on Monday, on the economy.
Mr Brown has previously warned the United Kingdom is at breaking point and could end unless the nations and regions get a real "voice" in decision-making.
Speaking in his daily Welsh Government press conference, Mr Miles said Brown
That went well didn't it ,"was prime minister at a time of difficulty in relation to the financial crisis, and so will bring a number of reflections from that first-hand experience".
Arguably Mr Brown introduced the whole concept of Austerity, and did his best to ito support a No vote in the Scottish Independence Referendum.
Will he look at and compare the powers the current Scottish Parliament has and used during the pandemic and how it intends using them in the recovery , with Wales and how the Westminster Government response was and its response likely another bout of Austerity once again under the cover of the "We are all in it together" mantra.
Conservative assembly member Darren Darren Millar accused the Welsh Government of "politicising its Covid-19 recovery group".
"The last thing that people in Wales need during this time of unprecedented crisis is another dose of Gordon Brown," Mr Millar said.Plaid Cymru's Delyth Jewell said:
"While I welcome the fact that the Welsh Government is already starting the work of post-Covid re-building, I hope they will reflect on what the road ahead requires, which is a complete and unambiguous dedication to forging the best possible future for Wales."Gordon Brown's experience may have a part to play in this, but I would urge Mr Miles to tell him to leave his ideological baggage at the front door and to brush up on his knowledge of Wales, so that we can sure it's the interests of Welsh citizens that are being served by his inclusion, not Mr Brown's well-known unionist mission."
Ms Jewell is spot on but even if Mr Brown was to take her advice and was to come up with idea that any Welsh recovery , will be dependent on the powers the Senedd (as it will be called by the time he and his "commision reports" will end up in the dustbin alongside like the Richard Commision (2002) and Silk (2011)
Prehaps YES Cymru should consider setting up a mirror group, to that let by Gordon Brown to approach the whole issue from another angle not that of one a ardent defender of the Union.