Jayne Rae, 53, from Whittle-le-Woods in Lancashire, died on Monday morning after a year with terminal breast cancer.
In a video first shared by Mr Corbyn on Sunday, Ms Rae told of arriving for hospital treatment to find a scene that “looked like Beirut”.
“I have never seen people lying in corridors covered in blood, dying, doctors under stress, nurses unable to help to the point of they were crying in frustration.”
She described tearfully how her mother was “begging” staff to save her life after she spent several hours waiting for treatment in “extreme pain”.
Following news of her death, Mr Corbyn tweeted: “Incredibly sad to hear that Jayne died this morning. Jayne’s life ended as she lived it: making the world a better place for others.
“Jayne sent me this video which shows her passion for defending our NHS and making sure it’s there for everyone whenever they need it.
Last week, Ms Rae’s daughter posted pictures to Facebook of a bunch of red roses sent by the Labour leader, along with a note reading: “Dear Jayne, thank you for all you do helping others. We will build a world of care for all. With our love and support, Jeremy x.”
Ms Rae had previously received media attention after holding a “last” birthday party in July to raise money for local community projects.
RIP Jayne became the top trend on Twitter on Monday afternoon as others paid tribute to the campaigner.