ABSTRACT Ultraviolet (UV) induced photoluminescence is widespread in Mammalia; however, its function(s) remain unclear. Most of the research to date has focused on the surface expression of photoluminescence (e.g., pelage), described qualitatively. Here, we report a quantitative assessment of photoluminescence of white‐tailed deer ( Odocoileus virginianus , herein deer) used for marking signposts. We analyzed 146 signposts, including 109 antler rubs on trees and 37 scent‐marking scrapes. We compared the spectra of signposts to the spectra of surrounding environmental features elicited by exposure to excitation lights peaking at 365 and 395 nm. Signposts showed significant contrast when compared to environmental backgrounds ( p < 0.001), and the resulting photoluminescence would be visible to deer based on previously described deer visual capabilities. This research is the first quantitative description of the functional use of environmental photoluminescence by a mammal and gives new perspective about how white‐tailed deer perceive their environment and communicate.