Trained immunity, an innate immune response characterized by enhanced cellular responsiveness, exhibits a profound memory akin to adaptive immunity. This phenomenon involves intricate metabolic and epigenetic reprogramming triggered by stimuli such as –glucan and BCG, shaping innate immune memory. Following elucidation of the background on trained immunity, it is important to explore its multifaceted roles in various pathological contexts. In this review, we delve into the specific contributions of trained immunity in the intricate landscape of viral infections, tumorigenesis, and diverse inflammatory diseases, shedding light on its potential as a therapeutic target, and offering comprehensive understanding of its broader immunological implications.