Creator Daron Nefcy originally conceived Star as a girl who wanted to be a magical girl like Sailor Moon and Marco as a boy obsessed with Dragon Ball Z and karate, with the two being enemies rather than friends. In this early version, Star had no actual magical powers and solved problems purely through determination.

Nefcy first pitched the show to Cartoon Network during her third year of college for its Cartoonstitute pilot program, but the network passed on it. She later pitched a revised version to Disney, where an executive suggested giving Star actual magical powers.

Nefcy originally placed Star in the fourth grade, inspired by her own childhood obsession with Sailor Moon, before later aging the character up to fourteen when pitching to Disney. The overall concept evolved over about six years.

Beyond Sailor Moon and Dragon Ball Z, Nefcy cited influences including the anime Magic Knight Rayearth, Revolutionary Girl Utena and Unico (which featured a blue unicorn), as well as Buffy the Vampire Slayer and indie comics like Scott Pilgrim and The Dungeon.

Nefcy deliberately avoided the typical magical-girl trope of hiding powers as a secret identity, instead having Star's schoolmates and Marco's parents already know about her magic from the start.

Each episode is storyboard-driven, with storyboard artists also writing the scripts by turning a two-page outline into a full script. Boarding an 11-minute segment required about 2,000 drawings completed within a six-week period.

Production moved animation studios over the course of the series: the first season was animated at Mercury Filmworks in Ottawa (which also worked on Wander Over Yonder) and then at Toon City in Manila, while seasons 2–4 were animated by Sugarcube and Rough Draft Studios in South Korea.

The theme song was composed by Brad Breeck, who also created the opening theme for Gravity Falls; Nefcy noted they didn't realize this connection until after hearing the song, since they listened to submissions blind. Composer Brian Kim was chosen from about ten candidates and gave each dimension in the show its own distinct musical sound inspired by indie rock from Los Angeles.

The show's title sequence was first shown at Comic-Con 2014, six months before its broadcast premiere, and fans uploaded the footage to YouTube, sparking early fan art and fan fiction.

The series premiere became the most-watched animated series debut in Disney XD's history, averaging 1.2 million viewers, and the positive social media reaction led Disney XD to order a second season six weeks before the show even launched on that network.