Mr Christie's family say he died on Saturday morning at Sydney's St Vincent's hospital.
"While no words can describe how crushed we are, Daniel fought courageously over the past 11 days which allowed everyone to say their farewells," the family said in a statement.
"It has also given us all strength and tightened even further the bond our family share."
The 18-year-old was taken to St Vincent's Hospital in a critical condition after being punched in Kings Cross on New Year's Eve.
His alleged attacker, Shaun McNeil, has been charged with causing grievous bodily harm, assault occasioning actual bodily harm and three counts of common assault.
Police allege McNeil, 25, struck three young men before targeting Mr Christie and his brother, Peter, when the other young men tried to hide behind them.
McNeil, a labourer, allegedly boasted he was a mixed martial arts fighter before punching Mr Christie in the face as he shielded the other young men.
Through his lawyer, McNeil has previously told a court that the first group of young men was trying to sell him drugs and he acted to protect his girlfriend who was with him at the time.
He was unable to explain his actions towards the Christies, police facts previously tendered in court said.
A court has previously heard that doctors believed Mr Christie would probably have suffered a serious brain injury if he survived the attack.
Police say they expect further charges to be laid against McNeil, who is next expected to appear in court in March.
Describing their son as a beacon of morality, the Christie family said they want to see "coward punches" become a thing of the past.
"People have the right to go out without experiencing mindless violence," they said in their statement.
"Therefore, if you are going for a night out, please honour Daniel's memory by thinking before you drink.
"Make sure your mates don't get carried away and do anything they'll later regret."
Mr Christie's organs will be donated.
"Although we are absolutely devastated at the tragic loss of our Daniel, we believe by sharing such a special gift with those in need, he is well and truly living on," the family said.
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