The father-of-two choked back tears as he spoke candidly about his fears that his spouse Susie Cleverly would not survive the disease.
Mr Cleverly, 53, was working as a minister in the foreign office in December last year when his wife was found to have triple-positive breast cancer.
In an interview with Sky News, the couple, who have been married for 29 years and share two teenaged sons, opened up about the difficult path they have walked.
Asked if he thought he could lose his wife, the foreign secretary became emotional and said: “I haven't thought about my mortality, and certainly haven't ever really given any thought to losing Susie, or what that might feel like — and then suddenly you get to confront that. And, we are close.”
Mrs Cleverly, 49, grew suspicious after finding dimpled skin on her breast.
The MP for Braintree had been on a train to Westminster when Mrs Cleverly called him to say the doctors thought it was cancer.
“I just burst into tears and I think I cried most of that day,” she said.
Mr Cleverly called his private secretary at the Foreign Office to request that his meetings be cancelled so he could return home to be with his wife. But when the aide asked whether everything was OK, the MP found himself speechless.
“I tried to say Susie might have cancer, I just couldn't get the words out, I couldn't speak — I like to talk, but I just couldn't speak,” Mr Cleverly said.
For the rest of the day he relayed the unfortunate news to colleagues by text.
Liz Truss, who was foreign secretary at the time and his boss, was “absolutely amazing”, he recalled.
He said friends and MPs from across the political spectrum have shown empathy to the couple throughout the process.
Looking back on the jolting diagnosis, Mr Cleverly said “I never felt anything like that before”.
Medical tests showed more than 12 lumps and a node in Mrs Cleverly’s arm. She said the discovery did not particularly faze her, but rather “the most frightening thing was the word ‘cancer’”.
The mother-of-two, who first met her husband while they were studying at university, was determined to fight the disease and “get on with it”.
She underwent a mastectomy and almost a year on from the diagnosis is still having immunotherapy to lower the risk of the cancer returning. Mrs Cleverly said that since the side effects of treatment had subsided she now feels “so much more like me”.