US prosecutors had sought 30 years for Pakistani-Canadian Rana, 52. Citing his poor health, his lawyers had sought a lighter term, saying he was duped into participation by his school friend Headley.
Rana was convicted in June 2011 by a federal grand jury, which found him guilty of helping LeT and planning an aborted plot to bomb the Danish newspaper Jyllands-Posten.
Rana, arrested in 2009 for his involvement in 26/11, was acquitted of that charge. However, Indian investigators want to question him for a second time.
“We have on one hand a very intelligent person capable and willing to provide assistance to many people... What is difficult to understand is how that person is sucked into a ghastly plot that proposed to go into the private office of a newspaper,” US District Judge Harry D Leinenweber said Thursday.
“Providing a long sentence would make sure that Rana does not get involved in any kind of terrorist activity in the future,” he added.