A jury returned its verdict on Mohamed Mohamud, 21, after deliberating for less than a day following the nearly three-week long trial over the attempted 2010 attack in the northwestern US state of Oregon.
Lawyers for Mohamud, who faces up to life in prison for plotting to use a weapon of mass destruction, claimed he was tricked into the attempted bombing by undercover agents from the Federal Bureau of Investigation.
But Oregon prosecutors insisted that the young man actively participated in a plot that could have killed thousands attending the Christmas tree lighting ceremony on November 26, 2010, had the bomb been real.
“Mr Mohamud made a series of choices over a period of several years – choices that were leading him down a path that would have ended in violence,” Greg Fowler, head of the FBI office in Portland, said after the verdict.
“His actions showed little regard for the rights and responsibilities that come with being an American or respect for the lives that he was prepared to take,” he added in a statement.
Speaking on the courthouse steps afterwards, prosecutor Ethan Knight said: “It’s good to have closure on the case.
“It’s also sad, in that this defendant’s conduct impacted a number of people including his family,” added the assistant US attorney, noting that the evidence showed there was “a significant threat and a dangerous situation.”
Sentencing was set for May 14 at the federal US District Court in Portland, near the scene of the crime.
Mohamud’s lawyers planned to appeal the verdict, according to The Oregonian newspaper.
In closing arguments on Wednesday, defence lawyer Stephen Sady said Mohamud, who was first contacted by an undercover agent a year before the attempted bombing, was a troubled teenager led on by the FBI.