The game was primarily developed by Ubisoft Québec, which had previously worked on Assassins Creed: Syndicate.[2] The concept for the game emerged in 2015, as the team was wrapping up development on Syndicate. In the shift to an RPG-esque game, inspiration was taken from titles such as The Witcher 3, Fallout, and The Elder Scrolls, in regards to the idea of player choice.[3] The development team engaged in communication with the team behind Assassins Creed: Origins; it was decided to quote:push [the series] forward with the introduction of RPG elements.[4] The setting of ancient Greece was chosen as it was one of the most requested settings from the fanbase.[5]

Odyssey uses a lot of the same graphical technology as Origins.[2] Far more color was used in the game; the designers tried to tap into the notion that the ancient Greeks believed that their land was built by the gods, thus the use of vibrant colors. There was pushback against the ordinary depictions of ancient Greece, which lean on it being an arid place with an emphasis on white and gold. The end result is intended to be a middle-ground between historical accuracy and vibrancy.[5]