Background: Urban greenspace has been associated with better health across a range of outcomes, such as mental and cardiovascular health. In contrast, research findings relating to respiratory health are heterogeneous. Several important pathways, such as lower exposure to air pollution, increased opportunity for physical activity, and reduced noise annoyance, may link greenspace with better respiratory health; however, these have not been sufficiently explored. Methods: In this thesis, I aimed to extend the knowledge base by completing a systematic review to assess the potential pathways underpinning urban greenspace and respiratory health, and also to synthesise the direction and magnitude of effect with different health indicators. Further, I analysed personal and home sensor data of air pollutants, physical activity, and noise with a suite of objective greenspace markers: the normalised difference vegetation index (NDVI), tree cover, and green land use. Study settings included urban centres in Europe and Delhi, India. Results: Many of the studies identified in the systematic review were positive (i.e., beneficial) with health, with the most consistent positive evidence for respiratory mortality. For the other indicators of health, particularly asthma, there was inconsistency in the direction and imprecision in effect estimates. In the European study, only NDVI was found to be associated with lower indoor concentrations of PM2.5. While there did not appear to be an indication of the relationship between greenspace metrics and indoor noise levels, there were clear reductions in the odds of reported road noise annoyance with NDVI and tree cover. In Delhi, PM2.5 reductions were weakly associated with NDVI and tree cover within trips, but only in the spring/summer/monsoon season; there was a suggestion of higher PM2.5 concentrations with green land use across trips. For physical activity, there did not seem to be an important relationship with average greenspace surrounding the home. Nevertheless, when quantifying the greenspace specifically in the environments where exercise occurred, there was a strong positive relationship again with NDVI and tree cover, and more so for cycling than walking. Conclusion: The empirical results of this PhD support several different pathways to health, with the exception of noise levels, with the strongest associations for physical activity. At the same time, findings were not universal: there were important nuances, for example, how and where the greenspace environment was characterised. In summary, my PhD research findings can assist with the interpretation of these specific underlying mechanisms related to epidemiological studies of greenspace and respiratory health.