Leow Wei Liang, who has autism and antisocial personality disorder, pleaded guilty to three out of seven charges of animal cruelty.
The remaining counts were taken into consideration during sentencing.
Injured cats slashed in Ang Mo Kio
Between April 25 and May 23, the National Parks Board (NParks) received complaints about cats in the housing estate appearing with slash wounds on them.
Leow admitted to causing the injuries after he was identified as the culprit.
Wanted to have fun with the "stray cats"
He said he thought about cutting the cats as he felt allergic to their fur.
He also said he "wanted to have fun since the cats were stray animals and not human".
Underwent IMH examinations
Leow was examined several times at the Institute of Mental Health in June.
He was found to have autism spectrum disorder and an underlying antisocial personality.
The NParks prosecuting officer told the court that Leow's "acts of cruelty" stemmed from "a simple desire to wantonly inflict pain and suffering on animals".
Leow's jail term was backdated to the date of his remand on June 9.
For each of his charges of animal cruelty, Leow could have been jailed for up to 18 months and also fined up to S$15,000.
About the case
On May 2, a white community cat with grey patches named "Miki" was found with a 15-cm cut on its back at the multi-storey carpark at Block 352A Ang Mo Kio Street 32.
On May 3, a black community cat named "Kopi" was found with a cut on its upper left abdomen at the SP Power Station facility next to Block 343 Ang Mo Kio Avenue 3.
And on May 19, a grey community cat named "Milo" was found with a 10-cm gash on the left flank at Block 343 Ang Mo Kio Avenue 3.