Playable cases are a new type of mixed-reality serious game (SG), combining elements of alternative reality games (ARGs) and education simulations to offer an immersive, transmedia story. Participants advance the plot through interactive gameplay and characters with the goal of creating products and experiencing real-world business situations. This study investigates the effectiveness of the playable case Microcore as a tool specifically for online writing instruction (OWI). Fifty students in online sections of a technical communication course participated in Microcore, in which they responded to pre- and post-survey questions and prompts directed at their perceptions about writing, understanding of workplace communication, and levels of engagement. Responses to the survey were collected, coded for thematic trends, and analyzed. Results from this survey study suggest that playable cases like Microcore may be effective at countering primary OWI difficulties, including disengagement, lack of social presence and humanity, faltering self-efficacy, and unclear, unproductive perceptions about writing assignments. Students responded positively to the playable case and appeared to develop more nuanced views about workplace communication and writing through this immersive narrative and interface.