The largest public space in any city is its streets. Investments which incorporate small-scale green infrastructure into streetscapes can bring more nature into the lives of urban residents worldwide, including those living in even the most economically and spatially constraint places. However, little is known about the impact of such small-scale investments on urban residents’ affective perceptions of their local environments and how to design these investments to maximise their positive impacts. In the current study, we use photo simulation techniques and an adapted form of the Positive and Negative Affective Schedule to examine the impact of small-scale green infrastructure interventions on the affective perceptions of low, middle and high-income sites in Santiago Chile. Our results, based on 62,478 reports of affective perceptions from 3,472 people, indicate that green infrastructure investments can both promote positive affect and, to a lesser, but still substantial extent reduce negative affect. The magnitudes of these relationships vary across discrete affective measures and for many of these measures, both positive and negative, a minimum of 16% increase in green coverage is required to see an impact. Finally, we find people associated lower affect with low, compared to middle and high, income sites but that these affective inequalities can be addressed, at least in part, through green infrastructure interventions.