The 'Summertime Sadness' singer, 27, performed for the couple at their Palace of Versailles reception on 23 May, the day before they married.
Rumours were rampant that Kanye had forked out a couple of million dollars to secure Lana's services, but she's denied that, saying she didn't charge.
When asked by a TMZ cameraman how much she'd charge to sing at his wedding, the singer replied: "I'd do it for free just like I did this one!"
She then added: "I would never let a friend pay me to sing at their wedding."
Lana's appearance at Kimye's pre-wedding bash had special significance for the couple as her song 'Young and Beautiful' was playing when Kanye proposed to Kim last year.
Kanye popped the question to Kim at a baseball stadium on her 33rd birthday in October 2013. He had the orchestra play Lana's gorgeous track during the big moment.
The rapper and his reality star love married in Florence, Italy on 24 May.
Guests enjoyed a week of pre-wedding entertainment - including the Versailles party - before being flown to Italy for the exchanging of vows.
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Watch Lana's music video for 'Young and Beautiful' below: