The Internet allows advocacy organizations to reach a large audience in an efficient way. When such advocacy organizations predominantly act online, they are termed dotcauses. Dotcauses play an increasingly important role in creating and maintaining social movements that are aimed at promoting sustainability. Yet, like offline social movements, dotcauses still need to exploit and mobilize resources, such as donations, media attention, and moral support, and they still need to be efficient and creative for the promotion of their social cause. Unfortunately, the social movement and social entrepreneurship streams of research have tended to produce separate literatures despite their potential synergies. We bring together both streams by using process models from social entrepreneurship and social movement theory to analyze the actions of dotcauses for sustainability. Additionally, we explore to what extent the Internet supports the actions of dotcauses and reveal which ethical considerations arise from combining entrepreneurship and activism. We collect data on eight dotcauses via semi-structured interviews and desk research. Our cross-case analysis reveals two types of dotcauses: online social entrepreneurs that partner up with firms and online entrepreneurial activists that target firms for protest. These two types differ substantially with regard to their collective identity and their ethical considerations. Our findings show that the Internet enables advocacy organizations to act in a more entrepreneurial and open manner. We suggest directions for future research, including a combination of social movement theory and social entrepreneurship theory to describe and explain the role of the Internet in processes of organizational change.