Background: Air pollution and greenness impact respiratory health, but intergenerational effects remain unclear. We investigated whether pre-conception parental residential exposure to air pollution and greenness at age 20-44 years is associated with offspring asthma outcomes in the Lifespan and inter-generational respiratory effects of exposures to greenness and air pollution (Life-GAP) project. Methods: We analyzed data on 3684 RHINESSA study participants born after the year 1990 (mean age 19, standard deviation 4), offspring of 2689 RHINE study participants. Modelled annual concentrations of particulate matter (PM2.5, PM10), nitrogen dioxide (NO2), elemental carbon (EC), and ozone (O3), and greenness (Normalized Difference Vegetation Index, NDVI) were assigned to parental residential addresses in 1990, corresponding to 1–18 years prior to birth (mean: 6 years, SD: 5). We analyzed associations using generalized structural equation modelling (GSEM), with cluster-robust standard errors allowing for intra-family correlation, while adjusting for potential confounders. Results: Among offspring participants, 18% reported lifetime asthma, 9% active asthma, 8% asthma medication, 5% asthma attacks, and 37% any asthma symptom. An interquartile range (IQR) increase in parental residential NDVI exposure was associated with less lifetime asthma (OR = 0.79, 95%CI: 0.64, 0.98 per 0.3 units). Similar associations were observed for active asthma and asthma medication use. Associations of air pollution with asthma outcomes were inconclusive. Conclusion: Parental exposure to residential green spaces before conception was associated with lower asthma risk in offspring. Urban planning policies prioritizing green spaces may be a key public health intervention for future cities.