The Cabinet minister was prompted by Tory backbencher John Lamont, who is supporting the campaign in his Scottish constituency.
The scarf was designed by Lochcarron Scotland’s Selkirk mill and the Selkirk committee of Cancer Research UK.
Mr Lamont, MP for Berwickshire, Roxburgh and Selkirk, praised the work of committee member Elaine Monro and others during Business questions.
“Elaine and some of her colleagues are in the gallery today showing off the wonderful scarf,” Mr Lamont said.
“Will the Leader of the House consider calling a debate on how the Government works and supports the excellent work of Cancer Research UK and other charities in fighting cancer.
“And will she agree with me that it’s a very fetching tartan which will no doubt raise lots of money for Cancer Research UK?”
As Ms Leadsom rose to answer the question, she unveiled her own tartan scarf, saying: “By sheer coincidence, this morning I decided to wear a pink jacket, and when (Mr Lamont) presented me with one of these wonderful scarves that Elaine and her colleagues have produced for Cancer Research, I was absolutely delighted to find that the chill in this chamber could be offset by something warm from Scotland.
“And I’m absolutely delighted with the contribution of all of those volunteers to Cancer Research, having had family members suffer from this terrible disease myself.
“I think we should all celebrate the excellent work of volunteers.”
Commons Speaker John Bercow said: “If I had known of the intention of (Mr Lamont) in advance, and of the sartorial plans of the Leader of the House, I would myself have worn a pink tie, of which I am proud to say I have several.
“But nevertheless, the important point is that the great cause has been eloquently highlighted, and that is what this place exists to do.”