In a new interview with The Guardian, the 'Goodbye My Lover' singer recounted first meeting the late Star Wars legend - Fisher portrayed Rebel Alliance agent Princess Leia Organa in the franchise - two decades ago at the Notting Hill eatery 192.
"I was going out with a girl whose parents were family friends of Carrie's and I sat beside her at lunch. I had just got a record deal and was moving to LA. Carrie's first question was: 'What do you do?' I said: 'I've left the army to go to make an album in LA,'" said Blunt.
"Question number two was: 'Where are you going to live?' I said I didn't know. Her reply – the third thing she ever said to me – was: 'Well, you're going to live with me.' So I did just that."
According to the Brit Award-winning artist, who served as a reconnaissance officer under NATO in the Kosovo War, he didn't encounter his famous landlady for an entire month after moving in.
"I'd get up and her mother, Debbie Reynolds, would shout: 'Hey Charlie – you wanna drink?' and I'd say: 'No, I'm James, thanks very much,' then head to the studio," Blunt continued.
Eventually, Fisher became more of a presence in the property, and the duo really hit it off.
"I came home one night and sat on the end of her bed and we talked until morning. After that, whenever I got back from the studio I'd go into her room to talk, no matter if it was 11pm or 3am. She became my best, best friend.
"I've got a song on my new album [Who We Used to Be] called 'Dark Thought', describing the moment when I went back to her house after she had died. I put my hand on her gate and started crying," he revealed.
At the age of 60, Fisher passed away in 2017, with the coroner ruling her cause of death as sleep apnoea. The condition doesn't allow air to enter the lungs properly during sleep or unconsciousness.
Reflecting on the loss of his great pal three years later, Blunt told PEOPLE: "The world is a sadder place without her. I lived with her in Los Angeles recording most of my albums, and whenever I've been in America, in LA, that has been my home.
"She was an incredibly inspirational, creative human being, who saw the funny side of everything. She was more fragile than I think people knew, but I was very lucky to know her."
"He'd never been to therapy and I've had enough for both of us, so we started talking quite deeply about his time in the army and the kind of impact that had had," Fisher revealed in 2006.
"We became very, very good friends by the end. He is a good person and he was very good to me when I had a friend pass away. He's a really good soul."
Watch: James Blunt paid £2,000 so his fans could have a drink at one of his gigs