The transvestite stand-up comedian held a fundraising gig for the Better Together campaign at Edinburgh's Festival Theatre on Friday night.
The one-off event also saw the launch of a new strand of the No campaign called "Scotland please don't go", which urges Scots to stay within the UK.
Izzard, who appeared at the launch alongside Better Together chairman Alistair Darling, said he expected to receive online abuse from aggressive Yes supporters - the so-called Cybernats.
But he said he felt very strongly that Scotland should remain as part of the UK and that he, as an Englishman, should be free to say so.
Speaking to the Sunday Herald before the show, he said: "I want to say this, but I don't want to push it really hard, because obviously some people are just going to hate me for saying this, and will not watch anything that I ever do again. I have to accept that. But I just feel that as a family member of the United Kingdom, I feel it would be wrong of me not to just say, 'Please don't go'."
A longstanding Labour supporter who hopes to become an MP or London mayor in 2020, Izzard admitted that part of his motive for volunteering for the show was to gain political experience.
"It is all experience for me," he said. "When I try and get elected, I would like to be someone who has experience, rather than just say, 'Hey, on Tuesday I thought I'd become a politician.' That didn't seem the best way of doing things."
The 52-year-old also said he would like to emulate the First Minister in politics.
"Alex Salmond? I think he's a very canny person. I think he's determined and he's been at this a long time ... When I get into politics I'd like to be a canny politician as well."
With the No campaign's lead narrowing, Izzard was asked if he felt the Yes side had momentum and might win on September 18.
He said: "I can't really sense that. A week is a long time in politics, as we say. And five months is an incredibly long time. I think it's everything to play for but, you know, I just hope Scotland stays with us."
Despite expecting a rough ride, Izzard received no heckling at the show. He largely steered clear of politics during his performance, although he did pay tribute to the late nationalist MSP Margo MacDonald.
The audience, a near full-house of 1900, also applauded when he said it was possible to be both British and Scottish and he wanted Scotland to remain part of the UK "family".
The spikiest moments of the night came from deadpan Stornoway comic Andy Todd, who brandished a copy of the SNP's White Paper on independence and ridiculed its contents.
Todd earned the biggest laugh for the joke: "I think Scottish independence is like a threesome. I think secretly we would all like to give it a go. We just don't want to do it with Alex Salmond."
Another line of Todd's came a close second: "I want to see Alex Salmond in charge of the economy as much as I want to see Nicola Sturgeon twerking".