There is growing recognition of the fundamental dependence of our urban systems on natural ecosystems. In this context, nature-based solutions (NBS) are gaining traction. NBS can help mitigate flood and heat risks, provide ecosystem services, and offer new or better green living spaces for humans and wildlife alike. While NBS offer a valuable method of urban climate adaptation, as a relatively novel form of infrastructure, they face a much wider variety of barriers to implementation than traditional ‘grey’ infrastructure. A key step to strategically overcoming such barriers is understanding them. This review is intended to establish a broad overview of existing literature about the barriers to implementing NBS in urban areas.