This study aims to investigate the linear attenuation coefficient and density of samples made of ferrophosphorus and typical aggregates, steel powder, and nanosilica powder in different ratios. Therefore, 60 concrete samples with dimensions of 15×15×15 cm and different contents of the mentioned materials were prepared. After the density was measured, the linear attenuation coefficients of the samples were measured by gamma radiation emitted from the cesium-137 source. The results showed that ferrophosphorus was the most effective factor in increasing the linear attenuation coefficient and the density of the concrete. After ferrophosphorus, steel and nanosilica powder – although much less than ferrophosphorus – increased the density and linear attenuation coefficient. The sample made of 100% ferrophosphorus aggregate and 20% steel powder without nanosilica powder had the highest density of 4395 kg/m3, and the sample made of 100% typical aggregate and 10% steel powder, without nanosilica powder, had the lowest density equal to 2269 kg/m3. The highest linear attenuation coefficient – 0.295 was related to the sample made of 100% ferrophosphorus, 30% steel powder, and 5% nanosilica powder. The lowest linear attenuation coefficient – 0.151 was related to the sample made of 8% nanosilica, without the ferrophosphorus and steel powder. The results indicated that the concrete density was directly correlated with the linear attenuation coefficient.