Prosecutor David Perry said the cleric made clear encouragements to kill when he gave lectures and sermons throughout London.
The jury, which had been given nearly 600 pages of transcripts of his talks, took nearly four days to reach a verdict, the Financial Times reported.
The Egyptian-born cleric, 47, faces a maximum sentence of life in prison.
Following his arrest in May 2004, more than 3,000 audio cassettes and 600 videos were found of inflammatory sermons intended for distribution. The sermons targeted Jews, non-believers, Western society, homosexuals, the tourist industry, the British royal family and women in bikinis, the BBC reported.
His lawyers are expected to appeal the verdict, CNN said.
Al-Masri also faces 11 terror-related charges in the United States and a postponed extradition hearing is expected to resume.