The impact of humidity levels on the absorption of moisture and mechanical properties of rock is crucial in safeguarding the rock against potential catastrophic failure in different humid environments. In the present research, the effect of relative humidity (RH) on Vesicular Basalts and Amygdular Basalts (VAB) collected from central and west-central India were investigated in laboratory on their uniaxial compressive strength, indirect tensile strength and the failure behavior. The samples of Vesicular Basalts and Amygdular Basalts (VAB) were subjected to various ageing conditions namely—saturated state and at relative humidity of 65, 75, 85 and 95% using environmental test chamber, before undergoing laboratory investigations. The aged specimen results were then compared with the results of unsaturated specimens. The mineralogical composition is also quantified by X-ray diffraction analysis. The vesicular basalts majorly consists of Augite, Albite, and Labradorite with the traces of clay minerals. It was observed that moisture absorption (%) was increased with the increase of ageing of the specimens, and that resulted in the reduction of strengths both under uniaxial and indirect tensile tests. Most of the specimens under indirect tensile test failed along the chain of vesicles, whereas the failure of specimens under uniaxial compression varied from axial splitting to shear mode with the increase of RH. In comparison with UCS, it is inferred that the presence of macro pores in small disc specimens has significantly contributed the failure along the chain of vesicles.