The disruptive development of digital technology and the rapid transition to a non-face-to-face economy caused by Corona Pandemic are accelerating the growth of online platforms. However, the market dominance of online platform companies leads to various unfair trade practices such as excessive fees, and the expansion into diverse business areas to build a platform ecosystem is considered to threaten the survival of small and medium-sized enterprises and small business owners. There are voices calling for regulating the abuse of market dominance and unfair trade practices of online platform companies in Korea as well as in Europe and the United States, and strong government-led regulations are under consideration. The enactment of the Online Platform Fairness Act and the revision of the Mutually Beneficial Cooperation Act, which are currently pending in the National Assembly, reflect this trend. However, government regulations have a problem that they cannot quickly reflect the rapidly changing market conditions. Not only is it difficult to clearly define the market, which is a prerequisite for regulation, and to verify the facts and effects of unfair trade practices, but it is also difficult to ignore the fact that online platforms contribute to the improvement of transaction efficiency and consumer welfare. Even if strong legal regulations can ensure fairness in transactions between online platform companies and their users, it is questionable whether this can resolve conflicts in a desirable direction and promote the collaboration among conflicting parties. The intrinsic nature of collaboration is the pursuit of diversity and harmony. A healthy and sustainable business ecosystem can be achieved by both large companies and SMEs collaborating to develop their own capabilities and build mutual trust. To this end, this study suggests the self-governance or self-regulation for online platform companies. In particular, it is believed that platform companies, based on the principle of ‘good faith’, should seek equity and fairness in their relations with users and quickly introduce in-house dispute mediation programs for resolving conflicts. Furthermore, beyond the collaboration with users or complementors, it is believed that platform companies should develop and practice social responsibility for the interests of society at large. More specifically, the suggestions of this study are as follows. First, based on the social interdependence theory and Deutsch’s theory of competition and cooperation, this study believes that the essence of collaborative (win-win) cooperation lies in harmony or balance between heterogeneous economic actors, and in order to achieve this in a conflict situation, it is necessary to seek cooperative-constructive conflict resolution rather than competitive-destructive conflict resolution. However, it is necessary to seek harmony between competition and cooperation in that it is possible to simultaneously pursue competition and cooperation, and fair competition or restrained competition can have positive results. Second, following Gorwa (2019)’s suggestion, this study also sees the appropriate balance between the self-governance, external governance, and co-governance as a good form of platform governance. In particular, as government authorities are strongly considering legal regulations, platforms are expected to strengthen self-regulation, establish an organization performing multiple functions ranging from investigating user complaints to creating ethical frameworks, seek user participation in policy decisions, and so on. Third, if a platform company wants to practice self-regulation, it must be made in the direction of complying with the ‘principle of good faith’ as in general transactions. The principle of good faith is closely related to the duty of cooperation, the doctrine of non-degradation from grant, and the principle of unconscionability. The core concepts that make up these principles include honesty, fairness, reasonableness, exclusion of bad faith and opportunism, compliance with fiduciary duty, respect of the other party’s rational expectations, and the implementation of community standards. Fourth, it is desirable to preemptively and quickly introduce an in-house dispute mediation program to resolve conflicts. Both the enactment of the Online Platform Fairness Act and the revision of the Mutually Beneficial Cooperation Act stipulate the operation of the public dispute mediation program as a means for resolving disputes between platforms and their users. In-house dispute mediation is a ‘low risk coordinative mechanism’ compared to public dispute mediation, which contributes to improving relations between disputing parties and enhances corporate reputation and image. In addition, it is a more efficient and flexible conflict resolution method in that new measures not recognized by the parties can be sought during the mediation process. Finally, platform companies’ collaboration efforts should be made in relation to consumers and society. The concept of collaborative cooperation requires platform companies to participate in solving social and environmental problems. It is necessary to consider how to impose responsibility on the platform and its various stakeholders to realize public values such as transparency and diversity.