The paper presents the effect of a viscosity modifying admixture (VMA) on the air permeability, sorptivity and strength parameters (compressive and tensile strength) of concrete. The Atlas VM-500 admixture used in the research is a well-known additive that is commonly applied in concrete technology. Air permeability tests were carried out using the Torrent method. It was found that viscosity modifying admixtures (VMAs) have a significant impact on the permeability of concrete. The lowest values of the ���� coefficient were obtained for specimens that matured in a water environment, and which contained 0.5% of VMA. This amount of additive reduced permeability by 34% when compared to the reference series of concrete. For air-conditioned specimens with 1.2% of VMA, the maximum decrease was 28% when compared to the reference samples. In the case of samples conditioned in an environment with an increased humidity, the maximum decrease occurred with a lower VMA content of 0.5% and amounted to 27% when compared to the reference samples. In addition, it was shown that the addition of 1.2% of VMA improved the compressive strength of concrete by 2.3% during its curing in water. In turn, this amount of VMA deteriorated its strength by 10.4% when the specimens were conditioned in air, and by 8.1% when they were conditioned in high humidity.