The series were originally announced in 2013 with Steven Spielberg attached as a producer. The show, initially set to premiere in 2015, remained in a development hell for many years as Rupert Wyatt and later Otto Bathurst were invited to produce. The casting took place between April and August 2019, with actor Pablo Schreiber cast as Master Chief, the main protagonist of the game series. Natacha McElhone was originally cast as Cortana; in 2020, the character was recast, with Jen Taylor, the voice and mo-cap actor for Cortana in all Halo games, was invited.
On February 24th, 2021, the series was moved from Showtime to the Paramount+ streaming service. On November 15th, 2021, the teaser trailer for the show premiered, followed by two trailers released on December 9th, 2021, and January 30th, 2022 (shown below, left and right).