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Abstract Evaporation of precipitation from plant surfaces, or interception, is a major component of the global water budget. Interception has been measured and/or modelled across a wide variety of forest types; however, most studies have focused on mature, second‐growth forests, and few studies have examined interception processes across forest age classes. We present data on two components of interception, total canopy interception (E_i) and litter interception—that is, O_i + O_ehorizon layers—(E_ff), across a forest age chronosequence, from 2 years since harvest to old growth. We used precipitation, throughfall, and stemflow collectors to measure total rainfall (P) and estimateE_i; and collected litter biomass and modelled litter wetting and drying to estimate evaporative loss from litter. CanopyE_i,Pminus throughfall, increased rapidly with forest age and then levelled off to a maximum of 21% ofPin an old‐growth site. Stemflow also varied across stands, with the highest stemflow (~8% ofP) observed in a 12‐year‐old stand with high stem density. ModelledE_ffwas 4–6% ofPand did not vary across sites. Total stand‐level interception losses (E_i + E_ff) were best predicted by stand age (R² = 0.77) rather than structural parameters such as basal area (R² = 0.49) or leaf area (R² < 0.01). Forest age appears to be an important driver of interception losses from forested mountain watersheds even when stand‐level structural variables are similar. These results will contribute to our understanding of water budgets across the broader matrix of forest ages that characterize the modern forest landscape.