This study aimed to evaluate the effect of adding pure calcium carbonate and eggshell powder to unsaturated polyester resin (UPR) on the linear absorption coefficient (μ) of gamma rays. This study is a continuation of a previous study conducted on samples of unsaturated polyester resin reinforced with pure calcium carbonate and eggshells to investigate the linear absorption coefficient of beta particles. With the increasing need for low-cost and environmentally friendly radiation shielding materials, this study explores the potential use of natural fillers, such as eggshells rich in calcium carbonate, as alternatives to traditional materials. A total of 39 samples were prepared with varying weight ratios (0.5% - 3%) of the added materials, and gamma radiation absorption was measured using a Geiger-Muller counter. The linear absorption coefficient values were then calculated based on the relationship between the sample thickness and the natural logarithm of the net counting rate. The results showed that both types of fillers improved the resin's ability to absorb gamma rays, with pure calcium carbonate demonstrating clear superiority in (μ) values across all used concentrations. Although eggshells contributed to enhanced absorption, the presence of organic residues and a porous structure limited their effectiveness. The study confirms that incorporating such materials can significantly affect the radiation absorption properties of composite polymer materials, thus supporting their potential use in sustainable radiation protection applications................. Key words:................ Radioactivity, linear absorption coefficient, polymer, Unsaturated Polyester Resin (UPR), calcium carbonate, eggshells.