The man is suspected of animal cruelty stretching back as far as November 2011, and which was carried out up until as recently as Wednesday, when a cat was found hanging dead outside its owner's home in the Frölunda neighbourhood of Gothenburg.
Police believe the feline was killed in nearby Högsbo, where six other cats had been tortured, slit open, and hung from trees in the past seven weeks.
The arrested man confessed to the crimes on Thursday, according to the Expressen newspaper.
"He has been detained and is in questioning, but we have no comments on what has been said," Björ Blixter of the local police told the TT news agency.
Further information has not been revealed as the suspect is very young and the investigation is in its very early stages.
In April, Högsbo residents organized a demonstration to voice their concerns and anger about the slew of killings.
"We want to push for the establishment of an animal protection unit within Gothenburg police," demo organizer Lotta Lagerström told the TT news agency
A 34-year-old man was arrested over Easter on suspicion of having carried out the gruesome feline killings, but was released after three days of questioning.