<p>Geo-sequestration of CO₂ is a key climate change mitigation technology witnessing rapid scale-up across the globe. With the potential to store CO₂ for thousands of years, deep saline aquifers are considered highly favourable, where the rock–brine–CO₂ interaction controls the effectiveness of the geo-sequestration. There are limited studies on the mechanical behaviour of sandstone saturated with brine solution of different salinity in the context of variable depths. Herein, with detailed experimentation, the influence of brine concentration was studied on the geomechanical properties of sandstone from Ib Valley coalfield in Odisha from three different depth ranges (100–150, 400–450, 800–850 m) belonging to different formations such as Kamthi Formation, Barakar Formation and Talchir Formation, respectively, of the Gondwana Supergroup. The effect of salinity on the mechanical properties of sandstones was investigated through a series of uniaxial compressive strength (UCS) and tensile strength tests with varying NaCl brine concentrations (5%, 15% and 25%). Furthermore, petrographic thin&#xa0;section and XRD analysis were performed to understand the mineralogical characteristics of the sandstone. The microstructural and compositional changes in sandstone were studied using a scanning electron microscope (SEM). The results reveal that depth, depositional environment, and brine concentration influence the strength and deformation attributes of the sandstones. Splitting longitudinal fracture with some shear component was the dominant failure mode. The dry samples showed higher UCS and elastic modulus than the saturated samples at specific depths. The samples saturated with higher NaCl concentrations (15% and 25%) had relatively higher UCS values and elastic modulus values than the lower concentration. Concentrated salt solutions can promote the precipitation of salt crystals within pore spaces, which may reinforce the rock matrix by partially clogging pores and increasing effective cohesion.</p>