Screenwriter Choi Ran was inspired by a real 2017 elementary school murder case in Incheon, South Korea; during the trial, the defendant showed no remorse and only lamented not being able to see cherry blossoms, which pushed Choi Ran to explore whether psychopathic killers could ever feel guilt and atonement.

In April 2020, both Lee Seung-gi and Choi Jin-hyuk were initially offered the male lead roles, and by June, Lee Seung-gi was confirmed to play the rookie police officer.

Rapper P.O was confirmed to join the cast in October 2020 after he was spotted attending a script reading session.

Actress Cheon Jeong-ha, who played Chi-guk's mother, passed away in 2021, making this her last drama role.

The first two episodes were rated 19+ under South Korea's youth protection law due to the graphic and unfiltered depiction of the murder of Ko Moo-chi's parents.

Mouse broke the record for the highest viewership ratings among all tvN Wednesday-Thursday dramas in more than two years and ranked first in its time slot among the 20-49 age demographic.

The finale achieved a record-high real-time online viewership rate of 90.6% on the Korean streaming platform TVING.

The series was selected for the 2021 Series Mania festival in Lille, France, where it had its international panorama premiere chaired by Florence Aubenas, and it was also featured in the 2021 K-format Virtual Screenings in the US held by KOCCA.

A Thai remake of the series, also 20 episodes long, premiered on TrueID on August 1, 2025, starring Shahkrit Yamnam and Chanon Santinatornkul among others.

Lee Seung-gi and Jo Jae-yoon (Daniel Lee) previously worked together on the MBC drama Gu Family Book, making Mouse their second collaboration.