This study aims to examine the effect of managers’ uncertainty on cooperative behavior in interorganizational relationships, and how this affects operational performance.  We conducted a survey with 225 Brazilian managers, and analyzed data using confirmatory factor analysis and structural equation modelling. Results present: a) a negative influence of uncertainty of state on operational performance; b) a positive influence of uncertainty of effect on uncertainty of response; c) a significant influence of uncertainty of response on cooperative behavior; and d) a positive influence of cooperative behavior on performance. The results indicated that cooperation and uncertainty accounted for 18.8% of the variability of operational performance. Considering the uncertainty that plagues Latin societies, this study can help to create more efficient ways to deal with the phenomenon. Rather than turning a blind eye to uncertainty, our study underscores it and treats it like another business environment issue.