Sir Michael Fallon attacked the Labour leader for calling into question Labour's commitment to the Trident nuclear deterrent, and for suggesting he would be reluctant to authorise a drone strike on the leader of the Islamic State terror group, and could suspend RAF attacks against the extremists in Syria and Iraq.
He said the "irresponsible" comments showed the Labour leader was presiding over "very dangerous chaos" that would put the nation's security at risk.
Sir Michael told ITV's Good Morning Britain: "I think you saw Jeremy Corbyn yesterday questioning strikes against terrorists, refusing to back the nuclear deterrent, he's been querying our Nato deployment and he seems to have fallen out with his own party over the nuclear deterrent.
"That's chaos, but it's very dangerous chaos that would put the security of our country at risk."
Labour has underlined its commitment to Trident renewal since Mr Corbyn used a Sunday broadcast interview to say he would order an immediate strategic defence review looking at "all aspects" of defence policy if he was prime minister after June 8.
Echoing a statement from a party spokesman issued after the interview, Labour campaign chairman Andrew Gwynne said renewal of Trident would be in the party's manifesto.
"Yes, it's Labour Party policy. We are committed to renewing the Trident system," he told BBC Radio 4's Today programme.
Sir Michael's comments signalled that the Tories intend to make Mr Corbyn's suitability for high office a key issue in the general election campaign.
But he was unable to stamp out questions over whether Theresa May will recommit to David Cameron's pledge not to put up to income tax, VAT or national insurance.
The Defence Secretary left the door open to tax rises, admitting the Tories do not want to commit to too many "prescriptive" targets in its general election manifesto.
Sir Michael said the Government could not rule out ordering a nuclear first strike.
He told the Today programme: "In the most extreme circumstances we have made it very clear that you can't rule out the use of nuclear weapons as a first strike."