Amos Yee, 18, shocked Singaporeans in March 2015 after posting an expletive-laden video attacking Lee as the founding prime minister's death triggered a massive outpouring of grief in the city-state.
He was jailed four weeks for hurting the religious feelings of Christians and posting an obscene image as part of his attacks on Lee, but served 50 days including penalties for violating bail conditions.
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He was jailed again in 2016 for six weeks for insulting Muslims and Christians in a series of videos posted online, but critics claim the real reason was to silence him.
Yee's lawyer Sandra Grossman of Maryland-based Grossman Law LLC said in a statement that US immigration judge Samuel B. Cole had granted her client's application for asylum.
"Yee has met his burden of showing that he suffered past persecution on account of his political opinion and has a well-founded fear of future persecution in Singapore," the judge said in the decision, a copy of which was seen by AFP.
"Accordingly, this court grants his application for asylum."
The judge said evidence presented during the hearing "demonstrates Singapore's persecution of Yee was a pretext to silence his political opinions critical of the Singapore government".
He also described Yee as a "young political dissident".
There was no immediate reaction from Singaporean officials to the decision.
Pro-democracy activists had been running a 'Free Amos Yee' campaign since his arrest. Source: AAP
The US Department of Homeland Security had opposed Yee's asylum application, saying he was legally prosecuted by the Singapore government.
Yee, a filmmaker turned activist, was detained by US authorities after he arrived in Chicago airport in December.
Phil Robertson of Human Rights Watch said at the time that Yee was a "classic political dissident" who deserved asylum.
He said Singapore "has subjected Amos Yee to a sustained pattern of persecution, including intimidation, arrest and imprisonment, for publicly expressing his views on politics and religion".
In Yee's video attacking Lee he compared the late leader to Jesus, saying "they are both power-hungry and malicious but deceive others into thinking they are compassionate and kind".
It was watched hundreds of thousands of times before being taken down from Yee's YouTube page.
WATCH: SBS's Insight program looks at free speech.
