Objectives: Infertility problems are seen in nearly 15% of married couples, and almost 50% of these involve male infertility. The sperm mitochondrion plays an important role in sperm motility. The morphology of sperm, sperm preparation techniques, and the number and motility of sperm during insemination are important parameters that affect the rate of pregnancy with intrauterine insemination. The aim of the study was to observe the changes in sperm mitochondrial activities and numbers with the Mito Tracker Red 580 kit at 30th, 45th and 60th minutes after swim up. Materials and Methods: In this study, we evaluated 20 oligospermic and 20 normospermic samples. The “swim-up” technique was applied to these oligospermic and normospermic samples, and changes in sperm mitochondria and number at 30, 45, and 60 min were observed using MitoTracker Red 580 staining. Results:The numbers of swimming sperm in oligospermic and normospermic samples were higher at 30 min than at 45 and 60 min. No marked change was detected in the mitochondrial activities of swimming sperm in oligospermic and normospermic samples at 30, 45, and 60 min after the swim-up. Our findings demonstrate that the number of swimming sperm decreased with time, but no change was seen in the mitochondrial activity of the sperm by the swim-up technique. Conclusion: According to findings, mitochondrial movement is not exactly related to the 30th, 45th and 60th minutes. Therefore, it is thought that it needs to be investigated in mechanisms other than mitochondrial activity. Bangladesh Journal of Medical Science Vol.18(3) 2019 p.479-483