Thin spray-on liners (TSLs) are surface support materials used in mining and civil engineering projects since 1990s with a wide ranging area of application from bolt/mesh support replacement to pillar reinforcement systems. This study presents the investigation of pillar reinforcement capacity of the TSL coated andesite rock core by compression test to mimic pillar reinforcement effect. The uniaxial compressive strength (UCS), modulus of elasticity (E), and energy absorbance capacity of uncoated and 5 mm coated cores having 25, 55, 75, and 100 mm diameters were compared. It was observed that there was no significant improvement in strength or stiffness for the homogenous rock cores coated with < 20% (TSL thickness to core diameter ratio) coverage. The main reinforcement contribution of the TSL was observed on post-failure region of the compression tests. Coated samples had higher energy absorbance (toughness) values than uncoated ones while the coverage of the TSL was increased, toughness enhancement also increased. Therefore, pillar reinforcement capacity of a TSL is a function of both pillar diameter and the TSL thickness. A new equation was found between energy absorbance gain for a given core dimeter and the coated TSL thickness. Researches or design engineers can use this equation as a guide to quantify the energy absorbance gain for a given pillar dimension and TSL thickness. It was found that the common on-site TSL practice of application of a fixed thickness (3-5 mm) for a given diameter does not contribute the toughness enhancement or pillar reinforcement.