The Prime Minister told his most senior political team that they "ain't seen nothing yet" if they thought the pre-election period was busy.
Mr Johnson's Cabinet is almost the same as it was before the vote, although Simon Hart has taken over from Alun Cairns as Welsh Secretary.
Speaking to his team around the wooden table in 10 Downing Street, the PM started by thanking his colleagues for their hard work during the campaign.
He said: "Good morning everybody, thank you very much, I want to welcome everybody back to the Cabinet table this morning.
“I want to thank you for all your hard work in getting this Government re-elected and getting this Government back 109 new Conservative MPs.
“The voters of this country have changed this Government and our party for the better and we must repay their trust now by working flat out to change our country for the better.”
He then extended a "warm welcome" to the new Welsh Secretary and also gave special mention to Culture Secretary Nicky Morgan, describing her as "a face you may recognise".
She quit the Commons at the election but was given a peerage and therefore allowed to continue as a minister. Is is thought ousted Richmond Park MP Zac Goldsmith could also receive the same honour so he remains as Environment Secretary.
Mr Johnson is expected to carry out a larger Cabinet reshuffle in February, once the UK has left the EU on January 31. This goal was key to Mr Johnson's "Get Brexit Done" campaign slogan.
He continued: “We should have absolutely no embarrassment about saying that we are a people’s Government and this is a people’s Cabinet and we are going to be working to deliver on the priorities of the British people.
“That’s what they want us to do and we must recognise that people lent us their votes at this election.
"It was quite a seismic election but we need to repay their trust and work 24 hours a day, work flat out, to deliver on this.
“Of course, the first 100 days were very busy, 140 days or whatever it was, you may remember it was a very frenetic time but you ain’t seen nothing yet folks.
“We are going to have to work even harder because people have a high level of expectation and we must deliver for them.”
The Prime Minister then began a call and response with his Cabinet, asking them: “How many new hospitals are we going to build?”
“40,” the ministers replied.
Mr Johnson then said: “Correct. How many more nurses are we going to hire?”
“50,000,” said the ministers.
“You know the answers,” Mr Johnson replied. “How many more police?”
“20,000,” the Cabinet said in unison.
Mr Johnson continued: “There is a huge huge agenda, a huge huge agenda, of delivering social justice, of addressing every problem from social care to homelessness to levelling up and uniting across our country with better infrastructure, better education and technology.
“That’s what we want to do, we’re Conservatives, we believe in extending opportunity across the whole of the United Kingdom and that’s what we’re going to devote ourselves to.
“Thank you all very much for your efforts, thank you for what you’ve done, I’m proud to say today that Saj has just passed me some, at the risk of sounding more North Korean than normal, Saj has passed me some good economic news that unemployment is up again, employment is up again and unemployment is down.
“The economy continues to be robust but we will now take steps to strengthen it further.”