Addressing the global biodiversity crisis requires conservation engagement across generations. However, generational amnesia and extinction of experience probably threaten this effort, reflecting declines in nature knowledge, experience and engagement among younger generations. We examined urban green area visit frequency, nature-relatedness, identification skills and familiarity with species (plants, birds and butterflies) and pro-conservation behaviour intentions in adolescents (15–17 years, mean = 15.97), young adults (18–29 years, mean = 23.72) and older adults (> 30 years, mean = 40.54) in Germany. With a path analysis, we explored relationships between concepts across all age groups. Although all age groups visited green areas similarly, identification skills, nature-relatedness and intentions declined progressively from older to younger groups. Nature-relatedness predicted intentions and identification skills predicted nature-relatedness across all groups. Our findings support the importance of fostering nature-relatedness and species knowledge through age-sensitive access to urban green areas with opportunities to connect with and learn about nature.