The scholarly interest for inter-firm arrangements that facilitate the potential of individual firms to develop and commercialize innovations has increased dramatically during the last decade. We contribute to this literature by arguing that opportunistic behavior of partners in contexts where cooperative norms are strived for has a u-shaped effect on firm innovation performance. Because of better prerequisites for crafting cooperative strategies, we argue that it is easier for a firm to perform better either in low levels of opportunism or in high levels of opportunism among partners. Further, we argue that action acquiescence moderates the relationship between opportunistic behaviour and firms innovation performance, such that the relationship between opportunistic behaviour and performance follows an inverted U-shape when action acquiescence is high, and a U-shape when action acquiescence is low. We base this on arguments suggesting that full acquiescence may leave the firm vulnerable for opportunistic threats (i.e., when opportunism is high) and for ineffective cooperation (i.e., when opportunism is low). Similarly, we argue firms to benefit from low acquiescence especially as it can serve to avoid previously mentioned threats.