The regional high court in the northwestern city of Celle convicted Ibrahim Rashid, 37, of seeking supporters for the Islamic radical network in web chat rooms between October 2005 and October 2006.
Presiding judge Wolfgang Siolek said the sentence should serve as a "warning signal" for other recruiters for banned groups.
The court found that Rashid had posted video recordings in which al-Qaida chief Osama bin Laden and other extremists urged attacks against the West on the Internet at least 22 times "and supplemented them with his own remarks."
He also uploaded videos showing car bombings and sniper attacks.
Siolek said the defendant was a "fanatical jihad fighter" and used the Internet "to create a global climate of fear of ubiquitous terror."
Rashid is the first person in Germany to be convicted under a law passed after the September 11, 2001 suicide hijackings by al-Qaida in the United States banning recruitment for terror organizations.
Previously, only belonging to a terror group and supporting a banned radical group with actions such as fundraising were against the law.
The defence had argued that Rashid only posted texts and videos that were already widely available and said the accused was not actively seeking new members for al-Qaida.
His lawyers said the case risked putting the German justice system on a slippery slope that could lead to "criminal law being broadened to cover laws on political convictions."
Although Rashid, who was arrested in October 2006, has already served half of his sentence, the court said he must remain in custody because he had shown no remorse and would likely attempt to leave the country if released.
"It remains advisable that he be deported after serving his sentence," Siolek said.
Rashid, a political refugee of Kurdish origin, arrived in Germany in 1996 and lived with his wife and four young sons in the western town of Georgsmarienhütte near Osnabrück.
An attorney for Rashid said he would appeal the verdict.