The jury in New York deliberated for two days before concluding yesterday that Hamza, 56, provided material support to terrorist organisations by giving a satellite phone to kidnappers of tourists in Yemen in 1998, supporting plans to open an al Qaida training camp in Oregon, and sending someone to an Afghanistan training camp.
"I never had 9/11 enter into my decision-making process," jury foreman Howard Bailynson said as he stood outside the Manhattan federal courthouse.
During the trial, jurors heard a tape in which Hamza said: "Everybody was happy when the planes hit the World Trade Centre."
Mr Bailynson said jurors relied on such factual evidence as a taped interview of Hamza conducted later by one of the hostages in the Yemen kidnapping rather than footage of him delivering the fiery sermons that attracted extremists to his London mosque.
Mr Bailynson, 44, said Hamza "was not tried on his words".
But defence lawyer Joshua Dratel disagreed, saying the verdict was "not about the evidence but about a visceral reaction to the defendant".
Sentencing was set for September 9, when Hamza, who was tried under the name Mustafa Kamel Mustafa, is expected to face a life term.