The Brown Tree Snake (Boiga irregularis) is native to Southeast Asia and Australia and has been introduced to Guam. There it causes major ecological and socioeconomic problems and is considered to belong to the 100 worst alien invasive species worldwide. We used a maximum entropy-based Climate Envelope Model to identify worldwide areas outside the species’ known range that are potentially suitable under current climatic conditions. Projections revealed that this invasive alien species potentially occurs in tropical and some subtropical regions. In the closer vicinity of the snake’s known distribution, highest suitability was found for the Northern Mariana Islands, Hawaiian Islands, Madagascar, New Caledonia, and Fiji Islands. If predictions are interpreted as depicting invasiveness potential of B. irregularis, strategies to prevent invasion should focus on these regions. An analysis of potential distributions under different future anthropogenic climate-change scenarios showed that the Fiji Islands, Hawaiian Islands, and Northern Mariana Islands will remain overall most suitable habitat for the Brown Tree Snake. In addition, we noted an increase of suitability in New Zealand.