Problem: Cardiorespiratory fitness (CRF) and mitochondrial function are important factors in health and disease. Even in immune cells, an effective metabolism is crucial for most major cellular functions, such as T-cell proliferation. Little is known about the relationship between CRF and mitochondrial metabolism of immune cells. Methods: In this narrative review, we collected the most recent literature in the field of exercise immunology and mitochondrial immune cell metabolism. We included studies, which used Oxygraph- or Seahorse techniques for measurement of mitochondrial function in various immune cell populations and subtypes associated with topics in the field of exercise in health and disease. Results: 20 studies were included in our analysis. Cell populations were PBMCs (peripheral blood mononuclear **cells), lymphocytes, T cells, NK cells, platelets, and neutrophils. While mitochondrial function was inconstantly affected through acute bouts of exercise, most of the studies, which included training interventions, reported a higher mitochondrial function in immune cells, which were in some studies correlated with the CRF. In various disease conditions, mitochondrial function of immune cells was impaired compared to healthy controls. › Discussion: If a regular exercise training is followed by an improvement in immune cell mitochondrial respiration, regular exercise could become even more important in the context of optimizing immune function and immune regulation in prevention and therapy.