Arch-Brexiteer Jacob Rees-Mogg and Vote Leave veterans Priti Patel and Dominic Raab joined discussions at the top table in Downing Street on Thursday morning.
Mr Johnson was flanked by Chancellor Sajid Javid on his left and Cabinet Secretary Mark Sedwill to his right.
For unlimited access to Scotland's best news, opinion and analysis SUBSCRIBE to Scotsman.com hereThe new Conservative leader told the room it was "wonderful to see this new team assembled here" which respects the "depth and breadth of talent in our extraordinary party".
"We are now committed, all of us, to leaving the European Union on October 31 or indeed earlier - no ifs, no buts.
"But we are not going to wait until October 31 to get on with a fantastic new agenda for our country, and that means delivering the priorities of the people."
Mr Johnson firmly stamped his authority on Government by installing Brexiteers into key positions.
And more than half of Theresa May's cabinet resigned or were sacked in a major overhaul of Government.
Mr Rees-Mogg, who as leader of the pro-Brexit Tory European Research Group (ERG) regularly proved a thorn in Mrs May's side, made his debut.
Having spent his prior career on the backbenches, he will now attend Cabinet meetings but Downing Street said he would not be a full Cabinet member.
Mr Raab returned to Cabinet as Foreign Secretary and effective deputy leader as First Secretary of State. He quit Mrs May's Government over her Brexit deal.
Ms Patel, who has advocated the return of capital punishment, was appointed Home Secretary.
She was previously forced to resign from Government by Mrs May over unauthorised contacts with Israeli officials.
Mr Rees-Mogg has denied Mr Johnson's new-look team was a "Leave takeover" and insisted the new PM was "bringing the country together".
But speculation has mounted that a general election is on the horizon because of the severity of Mr Johnson's clear-out and his installation of potentially divisive characters.
Mr Johnson could call a snap vote in order to break the deadlock in the House of Commons or a vote of no confidence could bring down his Government.