Asthma is a chronic inflammatory and heterogeneous disease developing mostly through allergic inflammation, which modifies the expression of various cytokines and neurotrophins. Previous studies suggest the involvement of interleukin (IL)-15 in the regulation of immune response in asthma. Brain-derived neurotrophic factor (BDNF) II plays an important role as a regulator of development and survival of neurons as well as maintenance of their physiological activity. Chronic stress associated with asthma and elevated IL-15 mRNA and BDNFII mRNA levels may affect the mood and a subjective sensation of dyspnoea-inducing anxiety. Psychopathological variables and numerous cytokine/neurotrophin interactions influence the formation of temperament and strategies of coping with stress. The aim of the study was to identify the role of IL-15 mRNA and BDNFII mRNA expressions and their effect on components of temperament and strategies of coping with stress in asthmatics. A total of 352 subjects (176 healthy volunteers and 176 asthmatic patients) participated in the study. The Formal Characteristic of Behaviour-Temperament Inventory (FCB-TI), Coping Inventory for Stressful Situations (CISS), Beck Depression Inventory, State-Trait Anxiety Inventory, and Borg Rating of Perceived Exertion (RPE) Scale were applied in all the subjects. The expression of IL-15 and BDNFII gene was measured using quantitative real-time polymerase chain reaction (qRT-PCR). Different levels of IL-15 and BDNFII expressions between healthy volunteers and patients were revealed in the study. IL-15 enhanced the BDNFII mRNA expression among patients with bronchial asthma. The depression level negatively correlated with the BDNFII mRNA expression. This neurotrophin modified the temperament variable. BDNFII significantly affected (proportional relationship) the level of briskness in asthmatic patients. BDNFII might influence the level and style of coping with stress (emotion-oriented style). This hypothesis requires further studies on protein functional models. The obtained data confirms the role of IL-15 and BDNFII in the pathomechanisms of depression and formation of selected traits defining the temperament in asthmatics.