Geological storage of hydrogen in saline aquifers can be important for a successful transition to a hydrogen economy. Molecular dynamics (MD) simulation was carried out to study the bulk and interfacial properties of the H₂+brine (NaCl), H₂+brine (KCl), and H₂+brine (CaCl₂) systems. The temperature, pressure, and salt concentration for the studied systems are in the ranges of 323-423 K, 14-150 MPa, 0-5.4 mol/kg, respectively. For H₂ solubility, the salting-out effect follows the order KCl< NaCl<CaCl₂. All MD results of the interfacial tension (IFT) agree qualitatively well with the predictions of the density gradient theory. Our computed IFTs of the H₂+brine (NaCl) system are also in reasonable agreement with the experimental results. The simulated fluid–fluid IFTs are obtained in the range of 45.2-80.8 mN/m for the studied systems. These IFTs are not significantly affected by pressure, and they decrease as a function of temperature. The higher the salt concentration, the higher the IFT. An important result is that the IFT values follow the order KCl<NaCl<CaCl₂. A negative surface excess is found for the ions, which explains the increase of IFT with salt content. The interfacial properties of the corresponding H₂+brine+silica (hydrophilic) system were also studied using MD simulation. The water CAs are obtained in the range of 42.5-72.2° for the studied systems. These water CAs are not significantly affected by pressure or temperature. The water CAs seem to follow the order KCl<NaCl≈CaCl₂. Overall, the IFT between rock and H is much higher than that between rock and brine for all conditions. H₂ is negligibly adsorbed at the interface between the water droplet and the rock. The capillary pressure of the H₂+brine+silica system was found to be higher than that of the CO₂+brine+silica system, indicating that CO₂ may be used as a cushion gas to withdraw H₂ stored in saline aquifers.