In the Finnish sawmill industry, inter-firm collaboration has often been brought up as a means of creating a competitive edge in global markets by achieving economies of scale. According to the resource-based view (RBV), a firm can evaluate its current or potential partners by considering firm-level collaboration as a portfolio of complementary strategic resources. The specific focus of the study is on examining the types and forms of sawmill co-operation, how the co-operation emerged and which firm-specific resources are mainly related to co-operation. Based upon this, we can see how the managers of medium-sized sawmills perceive network co-operation as facilitating the achievement of a sustainable competitive advantage. The empirical data for this study were collected by interviewing 16 managers and employees in medium-sized non-integrated sawmills, a joint-venture marketing company and other co-operative partners. The findings of the study show that meaningful and beneficial co-operation partnerships exist in the Finnish sawmilling industry, but the sawmill managers do not perceive this collaboration as a strategic resource. The marketing company was the only firm in this study that relied on its co-operative networks in seeking a sustainable competitive advantage. To make more of co-operative partnerships, the principles of co-operative networking should be understood better in the sawmilling industry in order to know what to expect from co-operation. Furthermore, the managers should have the courage to engage in more extensive co-operation in order for strategic rents to materialize. Since the selection of the right partners is fundamental, further studies could be conducted on the reasons behind failed or terminated co-operative arrangements to gather further empirical knowledge in this subject area.