The Interior Ministry said that the boy, an Austrian with Turkish roots, was arrested in the capital on February 10, the Austria Press Agency reported.
The arrest was triggered by tips to Austrian intelligence that a supporter of IS had posted stories and videos with Islamic extremist content on several TikTok profiles.
The suspect had a knife in his pocket at the time of his arrest, the ministry said.
During a search of his home, investigators found numerous Islamic extremist books as well as sketches of attacks with knives and machetes at a station and against police officers.
They also found handwritten instructions for making explosive material to serve as a detonator for a bomb.
Further material that apparently was meant to be used in making a bomb was found in the building's basement, along with other knives.
The suspect refused to testify in initial questioning.
APA reported that he apparently had planned an attack at the Westbahnhof, a major railway station in Vienna.
On Sunday, a teenager was killed and five other people were wounded in a stabbing in Villach, in southern Austria, by a man with possible connections with IS.
The suspect, a 23-year-old Syrian, was arrested after the attack on Saturday afternoon.
