Jose Pimentel, a US citizen born in the Dominican Republic who had converted to Islam, is in jail without bond for planning to set off pipe bombs across New York City and New Jersey.
He intended to target post offices, police cars and soldiers returning from abroad.
Police put together a video of what Pimentel is accused of trying to pull off.
Investigators say he tried to make a pipe bomb following instructions from a well-known al-Qaeda publication.
New York City officials say Pimentel is an al-Qaeda sympathizer and a follower of Anwar al-Awlaki, the radical American-born cleric who was killed back in September.
Mayor Michael Bloomberg says this is the 14th terrorist plot to target the city since 9-11.
None has succeeded.