Today's media ecology is in constant change due to rapid technological innovation, which is reshaping how social movement organisations (SMOs) use the media. Researchers have coined the concepts of 'media practices' and 'hybrid media ecology' to describe how activists give new uses to a range of online, offline, mainstream and alternative media practices. They have mostly examined grassroots networks against socioeconomic inequalities in Europe and North America and democratisation uprisings in Arab countries. In contrast, post-materialist movement experiences in South America have received scarce attention. Moreover, existing research on post-materialist movements elsewhere has made broad generalisations about them without engaging in their heterogeneity. This thesis aims to address these gaps by studying Chile as a single country case study and comparing the practices of its environmental and LGBTI+ SMOs. It strives to understand better in what ways and for what reasons SMOs have created new media practices in this context, and why these practices have varied across different SMOs. Based on informed grounded theoretical insights built from semi-structured interviews with SMO representatives, and triangulated with an analysis of documents, websites and social media accounts, the thesis makes three key arguments. First, it finds that nearly all the SMOs included in the study have created new media practices principally to reach more publics with the direct help of their constituents. However, there are some important differences regarding SMOs' organisational responses to this process. The thesis argues that a large minority of the studied SMOs are innovators that lead the development of new media practices, whereas another large minority emulate and indirectly expand these innovations. There are also a few cases of resistance to the media overall. Innovators seem either committed to inclusiveness as an end in itself or inclined to use citizen involvement as a means to gain political leverage, whereas emulators imitate trends in their field to remain current and appropriate. Thus, key to explaining these different objectives are SMOs' goals and resources. Finally, the thesis contends that innovation is much higher in the LGBTI+ movement while resistance only exists in the environmental movement. Political divisions, resource inequalities and geographical dispersion explain this. These findings make two important contributions to the literature. First, they show that variations across post-materialist movements should not be overlooked as they indicate the influence of the sociopolitical context on SMOs' media praxis. Secondly, the concepts of innovation, emulation and resistance help account for heterogeneity in how SMOs react to their media ecology and serve as conceptual tools for further comparative research.