Jun Maeda was born on January 3, 1975, in Mie Prefecture, Japan, and graduated from Chukyo University with a degree in psychology. Before finding success as a writer, he initially sought a career as a musical composer for major video game companies like Capcom and Namco, but was unsuccessful. This led him to focus on scenario writing for adult games, eventually working at the company Scoop on the game Chaos Queen Ryōko in 1997. He then moved to the brand Tactics, where he contributed to the scripts and scores for the games Moon and One: Kagayaku Kisetsu e. Following the positive reception of these titles, Maeda and several colleagues left Tactics to co-found the visual novel brand Key under the publisher Visual Arts.

At Key, Maeda became the driving creative force behind some of the most acclaimed visual novels in the medium. He is credited with pioneering the nakige, or crying game, a genre of story designed to deeply move the player to tears. His notable writing and composing credits for Key include Kanon, Air, for which he wrote most of the scenario, and Clannad, where he contributed approximately 75% of the writing. Other significant Key titles he worked on include Little Busters! and Tomoyo After: It's a Wonderful Life. He also wrote the manga Hibiki's Magic, which began in 2004.

In addition to his work on visual novels, Maeda is known for creating original anime series in collaboration with the animation studio P.A. Works and Aniplex. The first of these was Angel Beats! in 2010, for which he served as the original planner, writer, and composer. He followed this with Charlotte in 2015, and The Day I Became a God in 2020, taking on the same core roles for each series. His later work includes the original concept and music for the visual novel Summer Pockets, and the scenario and music for the role-playing game Heaven Burns Red, released in 2022.

Maeda personally composes much of the music and writes the lyrics for his projects, and his musical contributions are considered a key component of his storytelling. He established his own record label, Flaming June, in 2011. Several recurring themes appear throughout his works. A common element is magical realism, where fantastical or supernatural elements are introduced into otherwise normal settings, as seen in Air and Clannad. His stories frequently explore the bonds of family, particularly maternal relationships, and often blend comedy with tragedy to heighten the emotional impact of dramatic moments. He is also known for his personal love of baseball, which he incorporates into many of his narratives. His significant influence helped shape the visual novel medium and inspired a wave of successful anime adaptations that brought mainstream attention to the genre. In 2016, Maeda revealed he was suffering from dilated cardiomyopathy, a serious heart condition. Following the mixed reception of The Day I Became a God, he stated his intention to retire from writing stories for anime projects.