Mitochondrial activity is an important viability parameter of spermatozoa and is linked to sperm motility. Monensin is commonly used as an inhibitor for sperm mitochondrial activity in the laboratory. This study was conducted to evaluate the influence of some homeopathic dilutions of monensin on sperm mitochondrial activity. Fresh ejaculates from 6 mature bulls were used in the study. Samples of the semen were tested using a flow cytometer for mitochondrial activity and sperm viability using Rhodamine 123 and SYBR-14, respectively. The 9x dilution of monensin resulted in very highly significant (P<0.001) stimulation of mitochondrial activity. Monensin 5x, 7x, 8x and 13x caused highly significant (P<0.01) stimulation of the sperm mitochondrial activity. Other homeopathic dilutions of monensin (6x, 10x, 11x, 12x and 14x) also had a significant (P<0.05) stimulatory effect. The use of monensin did not have any negative effect on sperm viability. We conclude that some homeopathic dilutions of monensin increase mitochondrial activity of bovine spermatozoa without negative effect on sperm viability, the 9x dilution was the most effective. Further in vivo studies are required to estimate the effect of homeopathic dilutions of monensin on semen quality.