The present study summarizes and enriches the available information on the localities of Abies x borisii-regis Mattf. in Bulgaria. The information available in the three authorized herbariums in Bulgaria was analyzed: Institute of Biodiversity and Ecosystem Research - Sofia (SOM), Faculty of Biology of Sofia University (SO) and Agricultural University - Plovdiv (SOA), as well as from specialized databases. Personal data from newly established or confirmed localities of the species in Bulgaria were added to the available information. The results of the study summarize and supplement the information on the horology and ecology of Abies x borisii-regis Mattf. in Bulgaria. They also add new scientific information on King Boris Fir for which studies in Bulgaria are extremely few, especially in the field of ecological studies of the species.