In this study, the formative roles of common goals, equal status, integrative interactions, and authority support as the optimal factors for engendering individuals' cooperation with their proximal crossfunctional project workgroups are examined. The four factors are properties of the workgroup environment and each have been highlighted as being important in previous conceptual and critical success factors (CSFs) studies of project effectiveness. However, until now, there has been no systematic empirical test of the interactive effects of all four factors in a construction temporary multiorganization (TMO) workgroup setting. The four factors are conceptualized in this study as the reflective dimensions of a superordinate multidimensional latent construct, teamwork climate. An integrative test was undertaken of the construct validity of this multidimensional construct, its substantive utility relative to its dimensions, and of specific hypotheses connecting the multidimensional construct and its dimensions to individual's in-role, extrarole, compliance, and deference behavior; the test was performed using two cross-cultural samples of built environment professional managers (U.K., N=381; and Hong Kong, N=140) and structural equation modeling. The results showed convergence in support of the multidimensional conceptualization of teamwork climate, and also showed that teamwork climate significantly and positively influences workgroup members' in-role, extrarole, compliance, and deference behavior. These findings provide compelling indication that teamwork climate is an important and efficient determinant of cooperative behavior within TMO contexts and, in so doing, make an important contribution to the extant and construction engineering and management lines of literature on work climates. This study also makes an important contribution to the debate in the extant literature about how to model the four climate dimensions, in so far as it shows that a superordinate multidimensional conceptualization maximizes predictive utility, theoretical parsimony, and bandwidth. Finally, this study makes an important contribution to practice, as it focuses project managers' attention on creating the generative project environments for the four optimal conditions for teamwork.