Haroon Aswat, a Gujarati Muslim born in the UK had pleaded guilty to terror charges in March and has already served 11 years in a US jail.
Aswat from West Yorkshire in northern England could qualify for early release in six years.
"Aswat has been sentenced to 20 years in prison for terrorism offenses relating to establish a terrorist training camp in the United States," India-born Preet Bharara, Attorney for the Southern District of New York, and John Carlin, Assistant Attorney General for National Security, said in a joint statement.
"Aswat's conviction and the sentence imposed today-along with the other recent terrorism prosecutions by this Office, including of Sulaiman Abu Ghayth, Abu Hamza, and Khaled al Fawwaz-serve as further proof that justice in international terrorism cases continues to be delivered in American civilian courts," he said.
More From This Section
Aswat had admitted conspiring with radical Muslim cleric Abu Hamza al-Masri to set up a camp 15 years ago in Oregon.
Hewas supposed to provide religious training at the camp, which prosecutors said was set up to support Al Qaeda.
Speaking after the sentencing in the Manhattan federal court Carlin said: "Aswat was arrested more than 10 years ago, and his sentence is the result of the tireless and persistent efforts of law enforcement to hold accountable all those who wish to harm the United States, whether at home or abroad, no matter how long it takes".
In addition to the term of imprisonment, Judge Katherine B Forrest imposed a USD 200 special assessment. Forrest also ordered that Aswat be removed from the US to the UK following the completion of his sentence, it said.
He was arrested by UK authorities in 2005 at RAF Northolt, and three years later he was transferred from prison to Broadmoor psychiatric hospital.