Business people in the same industry adopt different levels of cooperation when dealing with suppliers for the same type goods. Many can be the drivers explaining this difference in behavior. This study aims to examine to what extent the perception of uncertainty of the manager (also called subjective uncertainty) influences cooperative behavior in interorganizational relations and how this behavior affects the operational performance of the firm. The theoretical justification and assumptions for this research are grounded mainly in the following references: Profit Theory of Knight (1921); Cooperative Behavior of Heide and Miner (1992); and the Relational View (Zajac & Olsen, 1993; Dyer, 1997, 1998). To analyze this theoretical proposal a survey was conducted with over two hundreds Brazilian managers from various industries. All measures were perceptual in nature. Measurement scales used in previous studies were adapted to collect the data, which were analyzed using Confirmatory Factor Analysis and then they were processed with the technique of Structural Equation Modeling (SEM). The Robust Maximum Likelihood method was adopted because it is recommended for the treatment of data from ordinal scales (Finney & DiStefano, 2006). This technique allows estimating simultaneously multiple dependency relationships among latent variables, in particular, when these variables influence (exogenous) and influenced a relationship (endogenous) in subsequent relationships (Fávero et al., 2009, Hair et al., 2009). The results point out to the multidimensionality of the construct uncertainty, characterized by the uncertainties of state, effect and response, in accordance with Milliken's proposal (1987, 1993). At the 5% level of statistical significance and statistical power of 99.8% was found: a) the negative influence of the uncertainty of state on operational performance, b) the positive influence of the uncertainty effect on the uncertainty of response; c) the significant influence of the uncertainty of response on the cooperative behavior; d) the positive influence of cooperative behavior in operating performance. The results also indicated that cooperation and subjective uncertainty explained 18.8% of the variability of operating performance, corroborating with findings of Jeffrey Dyer in field studies of Relational Vision.