BACKGROUND: Social mobilisation is potentially a key tool in the prevention of non-communicable diseases (NCDs) in fragile settings. This formative study addressed existing and potential social mobilisation mechanisms seeking behaviour to tackle NCDs in El Salvador, with an emphasis on the implications in the context of the current COVID-19 pandemic. METHODS: We conducted 19 semi-structured interviews with health workers, government officials, NGO leaders, and community members. Interviews addressed mechanisms for social mobilisation which existed prior to COVID-19, the ways in which these mechanisms tackled NCDs, the impact of COVID-19 on social mobilisation activities and new, emerging mechanisms for social mobilisation in the wake of the COVID-19 pandemic. RESULTS: Findings indicate a growing awareness of NCDs within communities, with social mobilisation activities seen as valuable in tackling NCDs. However, major barriers to NCD prevention and treatment provision remain, with COVID-19 constraining many possible social mobilisation activities, leaving NCD patients with less support. Factors linked with effective social mobilisation of communities for NCD prevention included strong engagement of community health teams within community structures and the delivery of NCD prevention and management messages through community meetings with trusted health professionals or community members. There are gender differences in the experience of NCDs and women were generally more engaged with social mobilisation activities than men. In the context of COVID-19, traditional forms of social mobilisation were challenged, and new, virtual forms emerged. However, these new forms of engagement did not benefit all, especially those in hard-to-reach rural areas. In these contexts, specific traditional forms of mobilisation such as through radio (where possible) and trusted community leaders - became increasingly important. CONCLUSIONS: New mechanisms of fostering social mobilisation include virtual connectors such as mobile phones, which enable mobilisation through platforms such as WhatsApp, Facebook and Twitter. However, traditional forms of social mobilisation hold value for those without access to such technology. Therefore, a combination of new and traditional mechanisms for social mobilisation hold potential for the future development of social mobilisation strategies in El Salvador and, as appropriate, in other fragile health contexts.