Brian K. Vaughan was hired to write a screenplay for Marvel Studios in May 2008, based on his Runaways. In April 2010, Marvel hired Peter Sollett to direct the film, and a month later Drew Pearce signed on to write a new script. Development on the film was put on hold the following October, and Pearce explained in September 2013 that the Runaways film had been shelved due to the success of The Avengers; the earliest the film could be made was for Phase Three of the Marvel Cinematic Universe. In October 2014, after announcing Marvel's Phase Three films without Runaways, Marvel Studios President Kevin Feige said the project was "still an awesome script that exists in our script vault…. In our television and Future film discussions, it's always one that we talk about, because we have a solid draft there. [But] we can't make them all."
Marvel Television, based at ABC Studios, was waiting for the right showrunner before moving forward with a television take on the characters. Josh Schwartz and Stephanie Savage, whose company Fake Empire Productions had an overall deal with ABC, independently brought up the property during a general meeting with the studio, and, by August 2016, the pair had spent a year conversing with Marvel about turning Runaways into a television series. That month, Marvel's Runaways was announced from Marvel Television, ABC Signature Studios, and Fake Empire Productions, with the streaming Service Hulu ordering a pilot episode and scripts for a full season. Hulu was believed to already have "an eye toward a full-season greenlight." Executive Producer Jeph Loeb felt "it was an easy decision" to have Hulu air the series over the other networks Marvel Television works with, because "We were very excited about the possibility of joining a network that was young and growing in the same way that when we went to Netflix when it was young and growing on the original side. It really feels like we’re in the right place at the right time with the right show." Loeb and Marvel Television were also impressed by the success of Hulu's The Handmaid's Tale, which helped further justify the decision. Schwartz and Savage wrote the pilot, and serve as Showrunners on the series, as well as executive producers alongside Loeb and Jim Chory. In May 2017, Runaways received a 10-episode series order from Hulu at their annual advertising upfront presentation.
Cast members and Schwartz and Savage appeared at New York Comic Con 2017 to promote the series, where a trailer for the series was revealed, along with a screening of the first episode. The series had its red carpet premiere at the Regency Bruin Theatre in Westwood, Los Angeles on November 16, 2017.
In May 2017, Siddhartha Khosla was hired to compose the music for the series. Khosla said that, due to his history as a Songwriter, his scoring process involves "working on these song-stories and weaving them through different episodes". He described the Runaways score as being "completely synthesized", utilizing analog synthesizers from the 1980s, specifically the Roland Juno-60 and Oberheim Electronics' synths. Khosla compared the "alternative feel" of his score to Depeche Mode, adding "There is an element of rebellion, so sonically going for something that is a little bit outside the box, non-traditional, I felt was an appropriate approach. I feel like I’m making art on this show." Alex Patsavas serves as music supervisor, having done so on all of Schwartz and Savage's previous series. On January 12, 2018, a Soundtrack from the first season consisting of 12 licensed tracks plus two by Khosla, was released digitally. Additionally, Khosla's original score for the series was released digitally on January 26.
Schwartz likened the tone of Runaways to that of the comics it was based on, calling it "so distinct", saying much of the tone Vaughn used when writing the comics overlapped with the tones Schwartz and Savage like to work in. The pair were excited by the freedom given to them by Hulu over the usual broadcasters they were used to working with, such as allowing the children to swear in the show, not having set lengths for each episode, and being able to explore the parents' story; Hulu wanted "something that felt broad and where we could push the envelope in places". Schwartz described the series as a coming-of-age story and a family drama, with focus on the characters that can lead to long stretches of the series not featuring super powers, so "if you didn’t see the show title, you wouldn’t know that you were in a Marvel show for long stretches ... That was our aesthetic starting place, but there are episodes where there’s some good [Marvel] stuff."
