In today’s competitive business market, firms that collaborate on a coopetition basis face obstacles in the form of decision-making, dependency, and trust in their competitor partners. This current study is the only one that has examined the relationship between coopetition and firm performance; yet, this relationship appears to be unclear due to the impact of trust and dependency on coopetition. This study investigates the impact of coopetition on firm performance by examining the mediating effects of decision-making and open innovation on firm performance. There are 230 sets of data that were collected from the employees of Chinese small- and medium-sized enterprises through the survey method, and the data were analyzed using Partial Least Square-Structural Equation Modeling. The findings of this study indicated that open innovation has a significant mediation effect between coopetition and firm performance, and that decision-making is also an important mediating effect in bridging the relationship between coopetition and firm performance. By considering these mediators, the findings revealed that the coopetition has a significant impact on firm performance through decision-making and has a significant effect on firm performance through increasing open innovation. The findings also revealed that decision-making played a significant role in mediating the relationship between coopetition and firm performance, which in turn specified a statistically significant positive relationship with decision-making that mediated a positive relation. According to the findings of this research, modern business firms should recognize the relevance of coopetition-based open innovation in their business processes to increase their overall performance. This study is significant because it provides a game-changing strategy for the management of businesses.