A court found him guilty Thursday of eight charges; six relate to "wounding religious feeling" and two are for his failure to turn up at a police station when summoned.
"He has, on several occasions, deliberately elected to do harm by using offensive and insulting words and profane gestures to hurt the feelings of Christians and Muslims," wrote principal district judge Ong Hian Sun in court documents obtained by CNN.
The moppy-haired 17-year-old will serve six weeks in prison and has been ordered to pay a $1,500 (2,000 Singapore dollars) fine.
A 'good deal'
Yee told CNN by phone that he'd been handed a "good deal" by the prosecution and said that he would not be acting outside the law in the future.
"I think that if I do continue to make critical social media posts I'll post things that aren't illegal," Yee, told CNN. "I think that will be possible."
Back in July 2015, Yee was detained for 53 days after he posted a tirade on YouTube
praising the death of Singapore's first Prime Minister, Lee Kuan Yew, calling him "totalitarian" and comparing him unfavorably to Jesus and Mao Zedong.
He was later sentenced to three weeks in jail but released given time already served.
Critics said Yee's arrest and subsequent detention highlighted the restrictions on free speech in Singapore. The Committee to Protect Journalists called for the teen's release.
Various social media posts created by Yee were presented as evidence against him in court.
"As his lawyer, I'm satisfied with the sentence and I've advised Amos not to appeal," Yee's defense lawyer Nadarajan Kanagavjayan, told CNN.
Yee had pleaded guilty to five of the eight charges.
"Given our situation and practices in Singapore, Amos' sentence is very fair because you must also remember that this isn't the first time he brushes the law," Kanagavjayan, told CNN.
Yee will begin his sentence on October 13.