Testosterone boosters (TB) are multi-ingredient dietary supplements that have gained popularity among athletes and the general population. However, certain ingredients in TB are associated with adverse events. The aim of the present study was to analyze dietary TB supplements available for sale online on shop.bodybuilding.com and amazon.com in ten distribution area markets. We evaluated the top five best-selling TB and the most frequently used ingredients of 50 selected TB and the evidence for their efficacy and safety, as well as legislation, statements in the European Union (EU) and sports organizations such as International Olympic Committee (IOC), International Society of Sports Nutrition (ISSN), Australian Institute of Sport (AIS) and World Anti- Doping Agency (WADA). Among 50 TB, 361 components and 98 ingredients were identified. The following ingredients were included in the final review: fenugreek, D- aspartic acid (DAA), 3,3′-diindolylmethane (DIM) or indole-3-carbinol (I3C), Eurycoma longifolia, Cordyceps spp., and ecdysteroids. In EU an authorized health claims refer to few ingredients in TB, mainly minerals, vitamins. Some ingredients were recognized by international sports organizations such as the ISSN, AIS, and WADA and some were identified as unauthorized ingredients/novel food in the EU. Selected ingredients can possibly increase the risk of endocrine system dysregulation.