18 Again is a South Korean television adaptation of the 2009 American film 17 Again by Jason Filardi, which itself was likely inspired by the 1988 comedy movie of the same name starring George Burns.

The series was directed by Ha Byung-hoon, who had previously helmed the similarly themed romantic fantasy drama Go Back in 2017.

18 Again was originally scheduled to premiere on September 7, 2020, but its release was postponed by two weeks due to the COVID-19 pandemic.

The main characters are direct counterparts to those in the original film: Kim Ha-neul's Jung Da-jung mirrors Leslie Mann's Scarlett O'Donnell, Yoon Sang-hyun's Hong Dae-young mirrors Matthew Perry's Mike O'Donnell, and Lee Do-hyun's Go Woo-young mirrors Zac Efron's Mark Gold.

Popular broadcasters Jun Hyun-moo and Jang Sung-kyu made special cameo appearances as themselves in episode 2, playing an announcer evaluator and an applicant during the JBC casting blind test.

The drama's original soundtrack was compiled into a two-part special album released on November 10, 2020, with the two CDs containing the theme songs and musical score separately.

Lead actor Yoon Sang-hyun himself contributed a track, 'Dasi Saranghandamyeon' (If I Love Again), to the OST as Part 8, released on October 20, 2020.