"Serious Sam 4" was announced under the name "Serious Sam 4: Planet Badass" in April 2018, during the opening of the Reboot Develop 2018 conference in Croatia, with a teaser trailer. One level was demonstrated behind closed doors at E3 2018 that June. At the time, the game was planned to launch in 2019. In May 2020, "Serious Sam 4" was re-announced without the "Planet Badass" subtitle and with a release window of August 2020 for Microsoft Windows and Stadia. According to developers, the "Planet Badass" title, which had borne out from the game's plot of a few Earthlings fighting against invading forces, was dropped as localizing this part of the title to other languages was impossible to do.