Al-Bahlul was convicted of 17 counts of conspiracy, eight counts of solicitation to commit murder and 10 counts of providing material support for terrorism.
Each count could bring life in prison.
The jury dismissed one count of conspiracy and one count of providing material support for terrorism.
FBI interrogators testified that al-Bahlul scripted the video-taped wills of two September 11 hijackers and made a two-hour al-Qaeda campaign commercial designed to recruit suicide bombers.
Al-Bahlul, who was brought to Guantanamo in 2002, is the second prisoner to go through a trial under the special military commissions system.
The first, former bin Laden driver Salim Hamdan, was convicted in August and sentenced to five-and-a-half years in prison.