Venâncio ‘Costa’ Sousa, who is originally from Madeira, Portugal, suffered multiple injuries in the incident near his home in Furbo at around 8pm on Sunday.
However, he was only discovered the following day lying injured in the garden of a nearby house at 11am.
He was taken to University Hospital Galway where he is being treated for head and facial injuries, broken ribs, internal injuries and a broken pelvis.
His shocked sister Mariana has flown over from London, where she lives, to be with her brother.
She described him as a “Portuguese guy, 49 years old” who had been working in Ireland for over seven years as a window fixer.
“‘Costa’, the name all his colleagues and friends call him, is a lovely, generous and happy person,” she wrote on a GoFundMe page set up to help pay for her brother’s care.
“On the last Sunday, October 24th, around 9pm, in Galway City, Furbo area, my brother was violently hit by a car that left (him) in (a) place between life and death.
“The driver fled the scene leaving my brother badly injured.
“He was found the next day around 12pm, inside the garden of a house near the crash site. He is currently in intensive care (ICU) at Galway University Hospital (private hospital) in induced coma and with life support for breathing.”
Shea also described his injuries that included a “broken pelvis, broken ribs, (injuries to his) bladder and swollen kidneys.
“He's got a lot of bleeding inner injuries, multiple head wounds from the impact and a lot of abrasions all over the body,” she added. “He's very sick in the hospital.
"In the coming days they will be very decisive for his life.
“Doctors can't give a prediction of what might happen. Have to be day by day.
His condition is very serious and right now all his family and friends praying for his life.
“At this time any help is important to save Costa's life, and I thank you from the bottom of my heart all those who can generously help.”
The page has generated just over 1,000 euro of a 50,000 goal since it was set up.
This afternoon, gardai said no arrests had been made and that investigations are ongoing.
“Gardaí are continuing to appeal for witnesses following a serious hit and run road traffic collision that occurred on the R336 Road between Furbo and Spiddal, Co. Galway on Sunday, 24th October,” they said.
Gardaí are appealing to any road users who may have camera footage (including dash-cam) and were travelling on the R336 between Furbo and Spiddal Sunday night, between 8pm and 9pm, to make this footage available.
Anyone with information is asked to contact Salthill Garda Station on 091 514 720, the Garda Confidential Line on 1800 666 111, or any Garda Station.