Recently, city science has been emerging as an autonomous field of research and making itself useful to the community through increasingly close collaboration between universities and local authorities, as evidenced by the creation of a European network of City Science Offices. On the other side, citizen science has been proven to be a powerful approach to addressing complex challenges by engaging ordinary people in scientific research and data collection and harnessing their collective intelligence. Both approaches can be useful for a wide range of urban challenges, but especially the second one emerged predominantly in the fields of ecology, biodiversity, and climate change. The aim of this paper is to demonstrate the use of these two approaches not only for scientific research in itself but also for the preservation of well-being and a healthy environment in the urban context, especially in medium-sized cities. The implications of adopting the approach proposed by this paper imply first of all that cities should equip themselves with research offices and dedicated technology infrastructure. Furthermore, local authorities should start developing policies based on the knowledge and data obtained through these tools.