This series marked Seo Kang-joon's first project after completing his mandatory military service, as well as his return to the small screen after the 2022 series Grid.

It was also Seo Kang-joon's first MBC drama comeback since Splendid Politics (2015), and his first MBC Friday-Saturday drama in 12 years since Hooray for Love and A Bittersweet Life.

In March 2024, Seo Kang-joon was reported to be in talks for the lead role, and by May 2024 Jin Ki-joo and Kim Min-ju were reportedly cast, with Jin confirmed as the female lead; MBC officially confirmed Seo and Jin as the leads in June 2024, and Kim Shin-rok's casting was confirmed in July 2024.

Kim Min-ju's character name 'Lee Ye-na' became a topic among her fans because it is identical to the name of Choi Ye-na, a member of the idol group Kim Min-ju previously performed in.

When the project was first announced, some viewers noted its premise evoked nostalgia for 1990s Hong Kong films like Fight Back to School and 2000s Korean films influenced by them, such as Undercover and My Boss, My Teacher, all featuring undercover police/agents posing as students.

The undercover-agent-as-student premise is also reminiscent of the American series 21 Jump Street, which began airing in 1987, and is loosely based on a real 1983 case in which an active police officer went undercover as a high school student for an investigation.

The school scenes were filmed at Chungang High School, located behind Changdeokgung Palace in Seoul; the campus's antique university-like architecture, including early 20th-century concrete arch-style structures visible in its corridors and stairwells, has made it a frequent filming location for other dramas such as Winter Sonata, Goblin, and Hospital Playlist's School Nurse Files spin-off.

In the story, the fictional Byeongmun High School was founded by Seo Byeong-mun, the secret keeper of Emperor Gojong's gold safe, echoing real Seoul schools founded by figures connected to the Korean Empire's imperial family, such as Hwimun High School (founded by Min Yeong-hwi) and Sookmyung Girls' High School/University (founded by Sunheon Hwanggwibi).

This is the first NIS-themed drama to air roughly four years after Black Sun.

Undercover High School was the first MBC drama to also be provided on the streaming service TVING.