Walking contributes to people's physical activity. While the physical environment (i.e., built and natural environmental characteristics) seems to be associated with people's neighborhood walking behavior, there is little evidence how these associations are moderated by age and vary across levels of urbanicity. This study examined the moderating effects of age and urbanicity on the associations between the neighborhood physical environment and the recreational and transportation walking of adults in the Netherlands. We used data on adults aged ≥ 18 years (N=65,785) taken from the Dutch National Travel Survey for 2015–2017. The outcome variable was the total duration of daily walking separately for recreation and transportation. We assessed the characteristics of the natural and built environments objectively based on respondents' home addresses within 300 m, 600 m, and 1000 m buffers. Tobit regression models with interaction terms between age and the physical environment were fitted. The results showed that age significantly modified the walking-environment associations and the moderating effects differed between weekdays and weekends. We also found that environmental characteristics (like residential density) correlated with walking differently among different age groups across urban and rural areas. Interventions intended to stimulate walking should be tailored to specific places and age groups.