Media convergence and transmediality have led fictional worlds originally developed in graphic novels to be expanded in more recent media such as video games, where environments and characters become playable and where storytelling elements intertwine with game mechanics and rules. This work aims to study the graphic novel saga Blacksad (Díaz Canales and Guarnido, 2001) and the video game Blacksad: Under the Skin (Pendulo Studios, 2019) in order to shed light on how the storytelling in the graphic novels is complemented by that of the video game, and what specific affordances of video games amplify the experience of the Blacksad universe. Both the graphic novel saga and the video game are analysed from the perspectives of media ecology, game studies, the foundations of transmedial worlds and the aesthetics of new media. Comics and video game coexist in a logic of transmediality and intertextuality that immerses users/players in a fictional world whose extension grows as they interact with their environments, characters and ethical codes, as well as with the different platforms and content generated by the community of fans or users.