Anticipating global interest in the sentence, the court allowed cameras inside to live broadcast Judge Kidd's remarks.
Cheers were heard outside court as the sentence was heard.
News.com.au reporter Rohan Smith said Pell stood emotionless in the dock as the sentence was read out. He signed paperwork for the sex offender register and bowed to the judge before being led away.
Pell entered the dock earlier flanked by five uniformed officers plus additional courthouse security.
He was not wearing the "Roman collar", a white band that goes around the neck of a priest.
The judge began his remarks by acknowleding that Pell was "one of the most senior figures within the Catholic Church globally" and a "publicly vilified figure" among some sections of the community.
"I am also conscious that I am sentencing at a particular time where in recent years there has been the exposure of child sexual abuse within institutional settings, including within the Catholic Church."
However, he said he was required to sentence him today in "accordance with the rule of law".
"As I directed the jury who convicted you in this trail, you are not to be made a scapegoat for any failings or perceived failings of the Catholic Church.
"Most importantly, while I must punish you for your offending, like anyone who falls to be sentenced by our courts, you are entitled to the balanced and steady hand of justice."
Chief Judge Kidd said Pell's attack was graphic and caused obvious distress to the victims.
Part of the evidence submitted was that Pell told one of the boys to be quiet as he was crying.
"Both victims were visibly and audibly distressed during this offending," the judge said.
"The obvious distress and objections of your victims is relevant to my assessment of the impact of your offending."
The judge said there was a "nasty element" to one of the acts that involved Pell taking one of the boy's head and placing the penis in close proximity to his head.
"The conduct here must have been particularly confronting and debasing."
He said additional force was used to push his penis into the other boy's mouth.
"There is an added layer of degradation and humiliation that each of your victims must have felt in knowing that their abuse had been witnessed by the other," he said.
"The offending which the jury has found you have engaged in was, on any view, breathtakingly arrogant."
Abuse survivors are breaking down in tears watching the live sentencing of Cardinal George Pell on a screen outside court. Emotions are high. A reminder... support services are available. @10Daily@10NewsFirst#pellsentencepic.twitter.com/VTnZxeozKp
The judge said: "In any event, Cardinal Pell, I find beyond reasonable doubt that, on the specific facts of your case, there was a clear relationship of trust with the victims, and you breached that trust and abused your position to facilitate this offending.
Even though there was no grooming, the judge said he thought Pell had made a "reasoned and deliberate decision" to engage in the first episode of offending.
"You had time to reflect on your behaviour as you offended, yet you failed to desist," Judge Kidd said.
The judge said the breach of trust and abuse of power made the offending significantly more serious.
"In my view, your conduct was permeated by staggering arrogance," he said.
"I consider in particular that the sexual penetration offence is very clearly a serious example of that offence and that the indecent acts encompassed by charges one and three are also serious examples of that offence."
Pell's age and good character considered by judge
Pell is 77 years old and Judge Kidd said his age was a significant factor in his sentencing.
"Of some real importance in my sentencing exercise is the fact that each year you spend in custody will represent a substantial portion of your remaining life expectancy," he said.
"I am conscious that the term of imprisonment, which I am about to impose upon you, carries with it a real, as distinct from theoretical, possibility that you may not live to be released from prison.
"Facing jail at your age in these circumstances must be an awful state of affairs for you. You are also clearly someone with some significant enough health issues.
"I have no doubt that you will experience some stress while in custody. I will make allowance for these matters."
The judge said he would also take Pell's character references into account.
"In addition to not having any prior convictions, I am satisfied that the evidence before me is that you are someone who has been, in the last 22 years, since the offending, of otherwise good character.
"I sentence you upon the basis that these episodes, viewed together, constitute isolated offending. I make substantial allowance for your good character and otherwise blameless life."
The negativity publicity and stigma is relevant
Judge Kidd acknowledged that the publicity surrounding Pell's case made the resumption of his earlier life, including his career, impossible.
"I accept the position of your parties and counsel in particular that I should make allowance for these matters in my sentence, and I have done so," he said.
The judge also accepted that Pell's situation was "somewhat unique" and the extremely high-profile nature of the case gave rise to security and safety concerns in prison.
However, the rejected that the broadcast of the sentencing would have a material impact on the publicity and Pell's experience in custody.
"These sentencing remarks would, in any event, have always been delivered orally in open court and would have been reported upon by the media without restriction," he said.
Campaigner against child sexual abuse, Leonie Sheedy, arrived at the court today hoping for justice.
"I hope that justice prevails and that Mr George Pell is treated like every other pedophile and sex offender in this state and he is incarcerated for a sentence that is appropriate to the crime that he committed," Sheedy told 3AW radio.
Cathy Kezelman from the trauma recovery-focused Blue Knot Foundation says the sentence represents the personal struggle for justice of many other abuse survivors and the outcome is likely to be emotional and polarising.
For some, any sentence won't be enough while others, still reeling from the verdict, will likely be outraged, she says.
"For too long, hermetically sealed systems of power, such as within the Catholic Church, have called the shots, protecting the church, its hierarchy and themselves," Dr Kezelman said.
"Hopefully this sentence can herald fundamental change to the church and other institutions, starting with accountable, responsible and transparent leadership, hierarchy and culture."
Last night as Pell prepared to learn his fate, a projection of the words "crime scene" lit up the gates to St Patrick's Cathedral where the sexual abuse took place.
As George Pell prepared to learn his fate, the words “crime scene” last night lit up the gates to St Patrick’s Cathedral where the sexual abuse of his two 13yo victims took place. I’ll be in court for Pell’s sentencing at 10am. @newscomauHQ Picture: @evo_lenspic.twitter.com/UgskvHlZRm