Elor Azaria entered the Israeli court with a wide smile and, flanked by his friends and family, continued to grin as his sentence was read out.
Throughout Azaria's trial and sentencing, judges pointed out he showed no remorse for killing Abdul Fatah al-Sharif.
They said the 19-year-old acted as both judge and executioner, but they found it was his first offence and he was acting within hostile territory.
The 18-month sentence is half of the minimum the prosecution had asked for.
But military prosecutor Nadav Weisman says justice has been done.
"The sentencing today sends an important message to all the soldiers and commanders in the army. As for the values of the military and the importance of protecting the purity of arms, it is clear to us that it is not an easy day for the defendent and his family, but justice had to be done, and justice was done. And this process had to happen, given the circumstances of the incident, and we are finishing the sentence today with a feeling that an important message was conveyed."
Abdul Fatah al-Sharif, a 21-year-old Palestinian, was lying unarmed and wounded in a street in Hebron last March after he tried to stab an Israeli soldier.
For 10 minutes, he lay motionless on the ground with his knife well out of reach.
Elor Azaria then, without explanation, walked over to Sharif and shot him in the head.
He later told his commander, "The terrorist is alive and needs to die."
Israel's military high command initially charged Azaria with murder before reducing it to manslaughter.
He was also demoted to the rank of soldier.
The attacker's father, Yousri al-Sharif, has called the 18-month sentence a joke.
"It's theatrical. It's unjust. It's a plea to shut us up. What's a year and a half? That time almost passed while he was in the military base."
But some Israelis say they believe the sentence was too harsh and have called Azaria a hero.
Prime Minister Benjamin Netanyahu had previously called for the soldier to be pardoned.
And outside the courthouse, parliamentarian Oren Hazan joined Azaria's supporters.
"By my point of view, every terrorist needs to finish every event with a bullet in his head. And when I say a thing like this, how can I not come out and support Elor Azaria? I hope that, today, (yes,) the court decided that he will go to jail, but I hope us, as politicians, as leaders, will do the right things and we will find a way to set him free."
Azaria's lawyer says he will appeal the sentence.
His supporters have welcomed that news.
"I'm the mother of soldiers, or fighters, just like him. How can I send my kids to the army now? I am going to send them. I am going to tell them to 'shoot to kill. You're a soldier, you have a gun, you are a fighter, that's your job.' He only did his job. That's what he does. That's what he did."
Issa Amro is a human rights activist in Hebron whose organisation the Camera Project was instrumental in documenting Sharif's death.
He says he believes the sentence for what Azaria did is not enough.
"Netanyahu himself invited his father for dinner, so I think Azaria will get a pardon. And the 18 months are not proportional to what he did. We are talking about a war criminal, according to the international law, who's getting only 18 months in jail and will get a pardon from his government."
In the past 17 years, Israel's military police have opened up more than 260 investigations into incidents where Palestinians were killed.
Only 17 have led to indictment, with Elor Azaria the only one convicted.
