He promised to campaign passionately for the interests of businesses to be protected and promoted. "We will make decisions and get stuff done," he said.
The government badly needed the business community to get behind them, he said.
Johnson is expected to win the Tory leadership contest by an overwhelming majority this week. City sources say as the likelihood of him winning has grown, he has made a concerted effort to woo big business at a series of similar events with senior figures.
Luminaries at last Tuesday's meeting also included Nigel Wilson, the boss of Legal & General; Alison Brittain, the chief executive of leisure giant Whitbread; and George Weston, chief executive of Associated British Foods.
The breakfast was held at the luxury five-star Beaumont Hotel in Mayfair and hosted by the financial public relations firm Tulchan Communications. City sources said it was orchestrated by former Conservative Party chairman Andrew Feldman, now managing partner at Tulchan.
Johnson, who was joined at the event by Health Secretary Matt Hancock, warned that they have more to fear from a Labour government led by Jeremy Corbyn. Without the support of Britain's biggest companies, Corbyn's chances of becoming prime minister would increase, he claimed.
Johnson once again talked up his track record as Mayor of London, claiming his policies dramatically improved the lives of the poorest during an eight-year term.
He said it would be his aim to achieve the same for the rest of the country but that would only be possible with a thriving economy that is able to fund the National Health Service.
Many of the executives present were said to have been impressed by Johnson's "energy and enthusiasm".
"What business really wants is an end to years of uncertainty and what they don't want is a Corbyn government. Boris could solve both those problems," one person said.
At a breakfast hosted last month by the public affairs group Brunswick, he also sought to distance himself from any hostility towards business, instead talking up the prospect of major tax cuts and his wider pro-business agenda.
He has also hosted a joint dinner with leadership rival Jeremy Hunt last week. Around 100 senior bosses of Britain's largest companies were invited to attend the banquet at a cost of £1000 a head. Invites offered an opportunity to "meet" and "hear directly" from the two candidates.