The aims of this study are threefold. First, the study aims to understand the main reasons that stop 18-24-year-olds from communicating condom use and safer sex. Based on findings supported by empirical studies in the literature and interviews with sexual health researchers in Canada, this study describes how a collaborative serious game integrates the principles of serious games with practices of safer sexual communication and negotiation. Finally, it includes an analysis of how 18- to 24-year-olds report practicing safer sexual communication and negotiation skills through participation in the collaborative serious game and what insights (a) 18-24-year-old participants and (b) sexual health experts share about the game that can inform future design iterations of this game. Forty participants aged 18-24 played the game and reported enhanced communication and language skills, raised awareness and reduced stigma around safer sex communication and condom use. The potential of the game in enhancing the participants' language skills (i.e., learning the language such as words, phrases, expressions) of communication and negotiation showed the highest frequency. Language skills and communications skills together comprised 28.5% of the overall feedback. The second most frequent theme was about the efficiency of the game in normalizing conversations around sex and condom use and removing the awkwardness around such topics. The game seemed to allow participants to practice dialogue and scenarios that extend beyond what they experienced in formal sex education in school. Participants also provided a range of recommendations for the next iteration of the game. To design the serious game, I followed a process of Design-Based Research (DBR) (Anderson & Shattuck, 2012) model and followed the four phases of DBR proposed by Reeves (2006). The study's findings aid other researchers in the field and offer insights to enhance sexual health education. With the increasing STIs in Canada, COVID-19's impact, and young people's reliance on online resources for answers, this research is timely. Moreover, the study contributes to the scarce research on collaborative serious games to improve 18-24-year-olds' sexual communication and negotiation skills. Limitations and implications of the design and of the game, as experienced by participants are discussed.