There are increasing signs that the space for civil society actions is slowly opening up in Vietnam. The existing studies have linked the changes in civil society action to the changing dynamics of state–society relations in one-party-ruled Vietnam. Yet, the majority of this literature has focused on the activities of NGOs. This article fills this gap by highlighting a high-profile case of civil society activism that is not centred on NGO actions. The Trees Movement is a broad-based citizen-led movement established to protest against Hanoi government’s arbitrary decision to cut down thousands of large old trees lining the city’s streets. I use this case study to argue that citizen-led activism, an emerging form of civic engagement, is likely to play a critical role in effecting change and (re)shaping state-society relations in Vietnam. This form of activism, if sustained, will encourage a move toward more deliberative and accountable politics in the same country in the long run. I also argue that environmental activism has opened up a new arena of contestation for civil society activism in Vietnam.