Mistletoes have a global distribution and are the largest group of parasitic plants living within the canopies of woody plants. In European forests, Viscum album L. ssp. album (common mistletoe) is a common sight and, despite being considered a pest, can play beneficial roles in the ecosystem. However, mistletoe infections are becoming more severe and widespread throughout Europe, including recent reports of large‐scale host tree mortality events. These mortality events are hypothesized to be a result of increased water stresses from severe mistletoe infections in tandem with drought. In this study, we estimate an additional water loss from mistletoe‐infected forests that has not yet been described: interception, or the storage and evaporation of rainfall. Results from rainfall simulations on mistletoes sampled from Gostynin Forest District (central Poland) indicate mistletoes can store 0.16–1.32 mm of rainwater. Inputting this additional water storage capacity from mistletoes into a rainfall interception model suggests that, depending on the severity of the infection, mistletoes could reduce annual rainwater supply beneath the canopy by 2–11%. In forests experiencing water stress from mistletoe infection and climate change, the rainfall interception by mistletoes represents an additional water loss of a magnitude worthy of future investigation. [ABSTRACT FROM AUTHOR]