He's allowed phone calls, visits and exercise.
"We are taking all of the necessary precautions to ensure Mr. Cosby's safety and general welfare in our institution", Corrections Secretary John Wetzel said in a statement.
Cosby also told his wife the prison officials have been ordered to keep a constant eye on him.
Bill Cosby feels ‘under attack’ after his 1st night in prison
SCI Phoenix offers multiple treatment and therapy programs, including one for sex offenders.
Cosby must spend at least three years in a Pennsylvania prison before he becomes eligible for supervised release, though he could end up behind bars for up to a decade.
At Cosby's first trial, prosecutors sought to call more than a dozen other accusers, but O'Neill limited them to just one: Kelly Johnson, who said Cosby drugged and assaulted her in 1996.
Glancing toward Constand and her family, the judge said her impact statement was crucial in determining the sentence.
The prison in Collegeville is about 30 miles northwest of Philadelphia and not far from the Montgomery County courthouse where the comedian was convicted of drugging and sexually assaulting Andrea Constand.
What happened to Cosby was "the most racist and sexist trial in the history of the United States", Wyatt also said before taking an even more odd turn in his speech.
If Bill Cosby is deemed at risk because of his celebrity or as a risk to others, he could be held in solitary confinement, and spending most of his days alone in a cell.
Meanwhile, TMZ reports that Cosby will be forced to pay his own legal bills in addition to service time in prison. Prosecutors convinced the judge to deny Cosby, 81, bail pending an appeal because they believe the elderly, frail and legally blind comedian still poses a danger to society.
Prisoners arriving at SCI Phoenix get a uniform, basic toiletries, linens, towels and state-issued boots, Pennsylvania Department of Corrections spokeswoman Amy Worden told CNN.
Constand went to police a year after waking up in a fog at Cosby's estate, her clothes askew, only to have the district attorney pass on the case.
Cosby's first trial past year ended in a mistrial when jurors could not reach a unanimous verdict.