Preserving biodiversity is a paramount global concern and, in this regard, monitoring urban biodiversity has increasingly taken on a significant role. Citizen science has emerged as a resource for addressing this challenge, offering a cost-effective approach capable of producing extensive data while promoting public engagement. In this work, a Lisbon university campus was used to determine the effectiveness of a citizen science project launched on the BioDiversity4All/iNaturalist platform to monitor urban biodiversity and analyse the influence of different engagement actions on biodiversity observations. The data analysis was based on biodiversity observations, including the temporal evolution of observations, the most frequently observed taxonomic groups, and the impact of promotional actions on project data. Additionally, the profiles of the observers were analyzed to assess their level of engagement and continued involvement in citizen science. The project had an effect on the increase in the number of observers and observations, and it was also possible to see a positive effect of the organized activities. The two indices used showed that Researchers and Students were the observer categories responding the most to the project, followed by Naturalists and Others. The results highlighted the capacity of citizen science to increase interest in biodiversity among both the university community and the general public. Furthermore, this work underlines the role of different strategies such as BioBlitzes, social media campaigns, and formal education activities to reduce the impact of relevant limitations associated with citizen science, namely taxonomic, aesthetic, and temporal biases.