Urbanisation has drastically reduced daily contact with natural environments, raising concerns about the health consequences of nature deprivation. Given the biological importance of sleep, these concerns are especially relevant, yet most existing studies linking greenspace and sleep rely on subjective data and imprecise exposure metrics. To overcome these limitations in our study, we investigated the link of daily nature experiences with nightly sleep outcomes (sleep duration, sleep efficiency and fragmentation) at the individual difference level, leveraging the high-resolution, repeated-measures design of objective data. A sample of 461 adults living in Stockholm County, Sweden, resulted in 3157 person-days with observations. Nature exposure was assessed using Global Positioning System (GPS)-tracked mobility and the Normalised Difference Vegetation Index (NDVI), while sleep outcomes were recorded through actigraphy. Multilevel mixed-effects regression models were used to evaluate associations, controlling for demographic, environmental, and behavioural covariates. The results indicated that higher daily exposure to greenness (NDVI ≥ 0.5) correlates with sleep duration. No associations were observed for sleep efficiency, while sleep fragmentation showed a minor association to longer time spent in higher greenness (NDVI ≥ 0.6) within 50-metre buffers. Gender and age moderated several relationships, with women experiencing greater benefits than men. Unlike their middle-aged (30-60-year-olds) counterparts, who saw a positive association, young adults (20-30-year-olds) saw a negative relationship between nature exposure and sleep duration. Noise exposure further influenced the strength and direction of the associations between nature exposure and sleep efficiency. By combining GPS, NDVI and actigraphy, this study advances the evidence base on environmental determinants of sleep and offers new insight into how urban nature can influence daily health outcomes. Findings underscore the potential for even modest greening interventions to improve sleep and promote urban wellbeing through low-cost, non-invasive public health strategies.