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The campaign, which aims to raise money for Evie - a young girl with a rare genetic condition - has so far raised over €100,000.
The event raised €12,000, and Conor agreed to put up the same amount.
Conor also donated a signed pair of gloves to the cause, which raised €500 and prompted one of the organisers to cheekily ask the former MMA champion to match the club's donation.
According to Crumlin coach Bra Brady, the champ had 'no problem' matching the sum.
Brady told The Mirror: "We got €500 (£429) for the gloves and being a bit cheeky I asked if he would match whatever we made and he said it was no problem."
Evie has a rare condition that saw her born without a large part of her X chromosome. She also has a condition called microcephaly with pontine cerebellar hypoplasia as well as a mutation of her CASK gene.
Basically, this condition causes a whole load of other problems including stunting the development of the brain, seizures, facial distortions, intellectual disabilities, and much more.
The condition isn't that well known in her native Ireland as it is uncommon. That means that if she wants treatment on her CASK genes, she'll have to be taken to America for a four-week-long programme with a specialist doctor.
Evie's mum Emma set up a fundraising page to try to gather the €60,000 that is needed. So far - helped by Conor McGregor's efforts - the page has raised €100,000.
Speaking to Irish Mirror, Emma said: "The time and effort put into the Crumlin boxing fundraiser was unbelievable and I would like to thank Katie, Sinead, Bra, Aaron and Phil and all involved in the club.
"They really went above and beyond on the day and we are forever grateful.
"It was not by any means a publicity stunt from McGregor as he did not even want to be mentioned, we can't thank Conor enough for helping our little girl.
"We can not get over how much our little community has pulled together to help Evie reach her target, with hitting well over her target this now means Evie can go to Virginia for very intense treatment in Feb 2020.
"I would like to thank every person who has taken the time to donate to our baby girl."
Crumlin Boxing Club recently held the event called 'Let's Sweat For Evie'. During that fundraiser trained boxing coaches held an intensive class and charged 40 people €20 to take part.
That's when they also raffled off the gloves.
All the money raised goes towards Evie's therapy and her journey next year to the Virginia Tech Carilion Research Institute Neuromotor Research Clinic for the treatment that she needs.
Her mum also told The Echo: "I just can't get over it. It's so emotional to see the little kids out going to hell and back and to see what an hour can do in Crumlin Boxing Club - the whole thing is just amazing."