Promoting mental health addresses a global societal challenge. Nature connectedness, or relatedness to natural systems, is associated with increased well-being and mental health. Among urban populations, nature connectedness has been reported as lower. Nature connectedness in urban settings has been somewhat overlooked by researchers. This cross-sectional online study addressed this issue by identifying socio-demographic predictors of urban nature connectedness among 165 students, aged 20 to 40, from the Technical University of Munich. Analysis of the data from 153 female university students was conducted using ordinal regressions, (a) separately and (b) merged with their 12 male counterparts. A separate gender analysis for males could not be performed, due to sample size limitations. Although access to nature and a considerable nature dose in terms of frequency and duration of nature contact were noted, possibly achieved through the engagement in outdoor activities, urban nature connectedness was rather low. Results showed that urban nature connectedness was negatively predicted by living in a rural area and positively predicted by engagement in outdoor activities and increased hours per week spent in nature. This information can help researchers operationalize the construct of urban nature connectedness. Furthermore, it can aid the development of interventions aimed at promoting urban nature connectedness, by encouraging urban inhabitants to (repeatedly) get in contact with and spend time in provided high-quality urban nature (e.g., during outdoor activities). To draw conclusions about causality, further research is required to identify a clear cause-effect relationship between socio-demographic characteristics and urban nature connectedness. Based on a researched dose-response relationship, a(n) (inter)national recommendation for the duration of nature contact should be established to promote urban nature connectedness and, therewith, health in urban inhabitants. Future research should also investigate further potential individual influencing factors, as well as gender and within/between-country differences among urban inhabitants.