Studies involving monozigotic (MZ) twins are of great importance for the understanding of genetic and environmental influences without the development of individual pathologies and pathways associated with lifestyle. In this context, discordance has recently been suggested in the levels of the brain-derived neurotrophic factor (BDNF) in MZ twins, which may be associated with the practice of physical activity (PA). The objective was to verify the relationship between the peripheral levels of BDNF and PA in MZ twins. This transversal and quantitative study included 11 pairs of MZ twins that answered the International Physical Activity Questionnaire (IPAQ), a brief anamnesis and were submitted to a blood collection (15 ml) for BDNF levels analysis, measured through ELISA kit according to the manufacturer’s instructions. The study was approved by the Ethics Committee of Centro Universitário Metodista IPA (no. 1.746.954). There was no statistically significant relationship between BDNF and PA levels in sedentary and physically active MZ twins (P=0.431). PA practice does not seem to influence BDNF levels in these individuals.