A member of the rival Sinn Fein, Michelle O'Neill, was picked as her deputy in the new cabinet.
"I see the hand of the future", Mr Johnson said.
There has been much speculation as to precisely how much extra funding will be provided to Northern Ireland as part of the New Decade, New Approach deal.
The British Prime Minister spoke in Stormont after speaking to DUP Northern Ireland Prime Minister Arlene Foster and her deputy Sinn Fein, Michelle O'Neill.
The news that same-sex marriage and abortion would be legalised in came in October 2019, as time ran out to restore a devolved government and stop the bill.
"I want to make it absolutely clear that we in the UK Government will now work with this revived government to ensure we deliver on that potential through better infrastructure, better education and technology", Mr Johnson told a press conference at Stormont.
As they posed for photographs Mr Johnson shook hands with Ms O'Neill and Northern Ireland Secretary Julian Smith shook hands with Ms Foster.
"We can not allow society to drift back and allow divisions to grow", DUP leader Arlene Foster said.
A general election is expected to be called this week as Taoiseach Leo Varadkar today meets Boris Johnson in Belfast.
"After three years, Stormont is once again open to business with a framework that can now move forward with improving people's lives and providing services to all communities in Northern Ireland", a- he declared.
DUP Agriculture Minister Edwin Poots warned that the money could be subject to "conditions", possibly due to an executive obligation to generate additional income through the introduction of water fees or an increase in interest rates.
"Using those three things to bring our whole United Kingdom together so all four nations benefit from the prosperity and growth we intend to deliver".
Top of the executive's in-tray is an industrial dispute in the health service that has seen nurses take strike action on three occasions in the last month. The pro-British Democratic Unionist Party has endorsed the plans to restart the institutions, which collapsed in February 2017 over a renewable energy initiative that spiralled far over-budget.
In the new deal, the Northern Irish assembly will decide four years after a transition period whether or not to keep the new customs arrangements.
The DUP lost support in the March 2017 election, but managed to remain the biggest party with a single-seat margin in the Northern Ireland Assembly over Sinn Fein.
The central government has promised to inject hundreds of millions of pounds into the NHS of Northern Ireland in the aftermath of the political agreement that led to the re-establishment of decentralized government.