Scott Franks, 31, says Leah Cambridge, 29, suffered three heart attacks after the operation at a cosmetic clinic popular with reality TV stars.
The beautician's death is believed to have happened due to complications which arose at the Elite Aftercare Clinic facility in Izmir, Turkey.
Her partner of ten years Scott said Leah wanted the op because she was self-conscious of weight around her stomach from giving birth to their three children.
Scott, of Leeds, West Yorks., said: "Leah was paranoid that she had excess weight from having three kids round her stomach.
"I told her she was beautiful how she was but she really wanted it for her own confidence.
"I didn’t think this would ever happen - or could happen to her."
Scott believes Leah's operation went wrong after fat was deposited into her blood stream and her oxygen levels dropped.
He says she was brought back to stable but she then had three heart attacks
He said: "Leah was under anaesthetic and complications happened due to fat getting deposited into her blood stream and her oxygen levels dropped.
"She was brought back to stable but had a further three heart attacks and there was nothing they could do after."
Scott, a scaffolding manager, has joined Leah's parents in Turkey to bring her body home.
He posted a heartbreaking video of himself wheeling her suitcase through the airport terminal.
Dad-of-three Scott, whose eldest son is aged 12, added: "This is going to be the hardest thing I've done - can't imagine being in the house without her."
Paying tribute, Scott said: "Leah was one in a million and I was so lucky to have her with me for ten years.
"Two days ago I was happy - now I'm a broken man.
"I know I’m moody and did her head in sometimes but I wouldn’t be where I am today without her is both guiding each other.
"Leah wanted to get married and we def would of in next few years but instead I’m gonna have to plan a funeral."
The procedure named the 'Brazilian butt lift' has grown in popularity after it was made famous by US reality TV star Kim Kardashian.
The procedure involves taking fat from the waist or stomach and inserting it in the buttocks - which gives women an hour-glass figure.
But Scott also warned others who were considering the cosmetic surgery to factor in all of the risks before going forward with any operation.
He added: "People need to be aware of the full situation that can happen with this treatment."
However, surgeons at Elite Aftercare say the but-lift is safer than other procedures because it involves using the body's own fat rather silicon implants.
The Elite social media channels proudly post pictures and videos of celebs eating treats and lounging by the swimming pool at their large villa hideaway while recovering from ops.
Ex on the beach, Geordie Shore and Towie reality stars have previously used the retreat for cosmetic enhancements.
Former Towie star Lauren Goodger successfully underwent a bum lift earlier this year.
Footballer Jamie O'Hara had a liposuction procedure at the facility in June and documented his experience on Instagram.
The clinic have been contacted for comment.