At a press conference on Sunday, Berlin's State Office of Criminal Investigations (LKA) said the arrest, which was made on Friday, dealt a key blow to crime.
"Without outside support from the Federal Police, it wouldn't have been possible in this way," LKA head Christian Steiof said.
The suspect is thought to have set 67 cars ablaze. Thirty-five others were damaged by the flames.
Steiof warned that the arrest itself would not put an end the problem of arson attacks, however. "The phenomenon, I'm 100-percent certain, will continue to keep us busy," he said.
The crimes were said to have occurred between June and August, particularly in three districts of the German capital: Mitte, Spandau and Charlottenburg.
Germany's Bild daily said the suspect was not arrested in the act.
Sources told the paper that the man had "very concrete recollections" of the incidents, including specific car makes and street names. Bild said he was not motivated by political convictions; instead, the suspect allegedly told investigators that he set the fires due to frustration over being unemployed at the time.
Police say more than 625 vehicles were damaged in arson attacks in Berlin this year, with more than 270 of those cases considered to be politically motivated.