Federal prosecutors said the 28-year-old German national, identified only as Volkan L. in line with German privacy rules, was arrested in Hamburg. He is suspected of membership in a foreign terrorist organization.
Prosecutors said that he traveled to Syria in November 2013 to join IS and underwent military training. They say he returned to Germany in March 2014 and turned his attention to finding new recruits.
He is accused of helping organize travel to Syria for one such person in summer 2014, acting as a go-between between the recruit and an IS member in Syria.
In a separate case, prosecutors said later Wednesday that they have indicted a 47-year-old German woman arrested in October as she attempted to return to the country after allegedly marrying an IS fighter and living in an Iraqi home seized by the extremist group.
The suspect, identified as Mine K., faces charges in a Duesseldorf court of membership in a foreign terrorist organization and having appropriated opponents property in violation of international law.
She is accused of marrying an IS fighter in a January 2015 video-call ceremony from Germany and joining him with her son in Turkey the next month. They ended up in Tal Afar in Iraq, where they lived in a house seized by the group, prosecutors said.
The womans husband was killed on guard duty later in 2015 and she decided the following year to leave IS, they added. She and her son left IS-controlled territory for Turkey, then returned to Germany last year.