The gut-brain axis is a term for the two-way communication between the central nervous system and the intestinal nervous system that controls the homeostasis of the gastrointestinal tract and connects it to the emotional and cognitive areas of the brain. Both the sympathetic and parasympathetic autonomic nervous systems and the hypothalamic-pituitary-adrenal axis participate in this complex communication. Recent researches emphasize the important role of the intestinal microbiota. One of the key components of the gut-brain axis is the vagal nerve, which collects information from afferent fibers from internal organs and then sends them to the brain, and with efferent fibers triggers the corresponding nerve reflex by sending feedback from the brain to internal organs. In this way, the vagal nerve connects different systems allowing their two-way communication. Recent research has shown that the intestinal microbiota plays an important role in the intestinal-brain axis given the possibility of secreting neurotransmitters and metabolites that stimulate nervous reflexes in the central nervous system and the intestinal nervous system. In addition to being able to have a beneficial effect on the gut-brain axis, they can also have an adverse effect that has been observed in neuropsychological and gastrointestinal disorders. The research on the intestinal microbiota has enabled a better understanding of the gut-brain axis and has become a topic of further research as well as a target for the development of new therapeutic strategies.