The study of the organism immune response in mild traumatic brain injury (mTBI) is an important stage in the formation of a scientific understanding of this type of brain damage. The purpose of the study: to research of the systemic immune response parameters in the experimental modeling of mTBI. The cellular composition and phenotype of immune cell subpopulations were assessed, and the content of pro- and anti-inflammatory cytokines in the mTBI and blood serum of injured rats was determined. A high content of leukocytes and interleukin 6 (IL 6) in the blood was found 2 hours after the injury. The number of cytotoxic T-lymphocytes and B-lymphocytes increased with a decrease of the neutrophils, monocytes, eosinophils and T helpers number one day after mTBI. During the indicated periods of observation, an increase in the content of cytokines TNFα and IL 6 in the cerebrospinal fluid and blood serum was observed, and the indicators of anti-inflammatory IL 10 increased 7–14 days after mTBI. On the 14th day after injury, the level of stab neutrophils remained low, while the number of CD45, CD3, CD20, and CD8 positive lymphocytes continued to increase, which indicates the progression of the inflammatory response. Thus, after the application of mTBI, an inflammatory reaction develops, accompanied by the manifestation of the activity of immune components. Cytokines are registered in the peripheral circulation and cerebrospinal fluid, the number of B-lymphocytes and cytotoxic T-lymphocytes increases.