"I love them. I consider them brothers in Islam," he said of the group responsible for the 9/11 attacks in the United States.
Adebolajo and fellow defendant Michael Adebowale, 22, are accused of murder in connection with Rigby's death, a brutal slaying that shocked the country. Rigby, 25, was walking near his barracks in south London in May when he was run over by a car, then stabbed and nearly decapitated.
The two suspects deny the murder charge, and Monday's hearing was the jury's first chance to hear directly from one of the defendants about what led to the attack.
Adebolajo laid out his life story, saying his parents were Christian and he used to read from the Bible, but he became frustrated and converted to Islam during his time at university. He said he had tried to travel to Somalia so that he could live under Sharia law, but was detained by Kenyan troops before he could get there. He also said that he had taken part in anti-war demonstrations, but felt that they were not effective.
The suspect was at times combative toward the prosecutor, but remained unemotional until he spoke about his family.
"I love my wife. I love all my children very much. It's very difficult to leave them. But every soldier has to go through this," he said.
Turning to the attack, he said that he was not motivated by any personal grievances against Rigby rather the plan was just to find a British soldier. He said that he made sure that Rigby was a soldier before he killed him, and hoped the death could "indirectly save the lives of many."
"I was keen that the reason for the death of this man is not misunderstood. I wanted people to understand. ... It only happened for one reason only, and that is foreign policy," he said.
Adebolajo said he stayed at the scene waiting for police to arrive, then rushed at them because his religion forbade him to run away from the enemy. He denied a charge of trying to kill a police officer.