He said that it is "undeniable" that advancements have been made, particularly "major, major improvements" in cancer care and a boost to cardiac treatment.
"The patient experience is immensely more positive then the general perception," Mr Blair added.
But the prime minister acknowledged that "challenges remain" and there is a "great deal of work to do" to persuade people to support planned reforms to the NHS.
His comments follow a period of great unrest in relation to NHS planning, workers' pay and the new recruitment schemes introduced for trainee doctors.
On Saturday the chairman of the British Medical Association wrote to Mr Blair, calling on him to deal with the recruitment problems, which have led to some junior doctors saying they will leave the NHS and go abroad if they cannot get a training placement of their choice.
In the past few weeks the Royal College of Nursing and Unison have warned that they are considering industrial action to force the government to reconsider the pay package proposed for health workers earlier this year.
And earlier this year a report from the health select committee said that a "disastrous failure" of workforce planning has led to the NHS turning from "boom" to "bust".
But, Mr Blair said, if people look back at the last ten years, the NHS "has got better".
"Yes it is an enormous challenge," he added. "But… in my job you have to be an optimist, but if you think about the challenges we face, and where the service is happening, at least we're having an argument about how to improve it, not how to prevent it from collapsing. That is a real change."
Norman Lamb, Liberal Democrat spokesman, has dismissed Mr Blair's confidence in the NHS, arguing that his comments this morning are nothing but "spin".
"In 1997, Tony Blair said that we had 24 hours to save the NHS. Ten years later we have a prime minister trying to spin his way out of the crisis in the health service," he said.
"Anyone who has used the NHS can see what's wrong with it: too many central diktats which leave hospitals in debt as they are forced to prioritise political targets rather than patient care."
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