This research was conducted to investigate the potential of T. stromaticum as an endophyte of cacao and its possible activity as an inducer of resistance against M. perniciosa and as a promoter of plant growth. Experiments were conducted on sterile and nonsterile environments to study the ability of T. stromaticum to endophytically colonize cacao. Bean seedlings were used for comparison purposes. Field inoculations were carried out to study the recovery of T. stromaticum from adult cacao trees. Electron microscopy and culture on agar media were used to verify endophytic colonization. Resistance to M. perniciosa was studied by inoculating the pathogen and the mycoparasite on cacao seedlings in greenhouse experiments. Finally, Northern blot studies were conducted to verify the expression of selected genes involved in plant defense, gene regulation, and energy production.