Co-creation platforms are virtual platforms dedicated to a variety of contests launched by a seeker of a particular solution (e.g., brands). These contests are solved by different participants (e.g., individuals) having distinct skills, background, and resources (e.g., knowledge, time). These platforms are characterized by conflict of interests and uncertainty, and they are a place where everyone try their best to achieve their goals. As such, different behaviors may take place. This study focuses on opportunism which is one of the most prevalent and inherent behavior in co-creation platforms. Building on co-creation platforms and opportunism literatures, we investigate the role of opportunism in co-creation platforms. By using the method of Netnography in one of the leading international co-creation platforms, we found that opportunism could be constructive and destructive at the same time. Theoretical and practical implications are presented.