Nature-based solutions (NBS) are essential for carbon-neutral cities, but the question remains how to allocate them effectively. Carbon neutrality requires city-led climate action plans that include both indirect and direct NBS contributions. Here, we assess the potential of NBS to reduce carbon emissions in European cities, focusing in particular on commonly overlooked indirect pathways, such as interventions in human behaviour and resource conservation. Assuming maximum theoretical implementation, NBS in the housing, transport and industry sectors could reduce urban carbon emissions by up to 25 %. Spatial prioritisation of different types of NBS in 54 large cities in the European Union could reduce anthropogenic carbon emissions by an average of 17.4 %. Combining NBS with other existing measures in the Representative Concentration Pathway scenarios could reduce total carbon emissions by 57.3 % in 2030, through both indirect pathways and sequestration. Our results suggest that carbon neutrality will be close to 2030 for some pioneering cities, with three achieving it completely. (Haozhi Pan, Jessica Page, Zahra Kalantari, Nature)