The quirky singer recently opened the famous hat designer's first catwalk presentation in a decade and paid homage to Blow by wearing one of her dresses.
Treacy revealed that the collaboration was the fashion-loving Born This Way star's idea - and he was thrilled to have her on board.
"I went to see Lady Gaga backstage after seeing her at Twickenham [for the Born This Way Ball tour], and I was telling her about the show and then she just suggested it. It was all her idea. She was going to be in Dublin the night before, so she said that she'd fly over for it. Playing to 80,000 people on one night and then appearing in my show the next? Amazing. Of course I agreed," he told Vogue. "She had this whole concept, she said she was feeling like Isabella. She rang me on her way to the show to apologise for being late - you never see that any more. She really is like a 21st Century pop version of Isabella Blow."
Treacy also praised Gaga for her unique take on fashion.
The singer is known for her eccentric outfits and her perception of style allowed the milliner to go all out with his designs.
"She's a really fun person to work with," he continued. "She has a different sensibility - a different idea of what's perfect and beautiful. She allows me to be really creative and brings my designs to a whole new audience."
COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? firstname.lastname@example.org