Research using subjective wellbeing (SWB) measures finds that the greener an individual’s local environment is, the higher the levels of happiness and the lower levels of stress they tend to report experiencing. This literature presents positive associations between existing large-scale green spaces, such as urban parks or squares, and the wellbeing of residents living in close proximity to them. In contrast, in the current work, we present a novel approach which combines SWB measures with photo simulation in order to examine the impact of street-level green infrastructure interventions on the people’s perceptions of the SWB associated with urban sites. We tested the approach with the attendees of the 20th Biennale on Architecture and Urbanism in Chile in 2017, exploring the impact of four different types of street-level green interventions. The results indicate that all types of green interventions considered significantly increase the perceived happiness and reduce the perceived stress associated with the sites during short exposures, with varying effect sizes across different types and scales of interventions. The proposed technique could be used in urban planning processes to examine the potential SWB benefits of green infrastructure investments prior to their being rolled out.