Recently, due to application of nuclear technology and the issue of protection against nuclear radiations with harmful environmental impacts such as gamma rays, heavyweight concrete is widely used in industry. On the other hand, water to cement (w/c) ratio is one of the chief factors affecting concrete behavior. Thus, in the present research, it has been attempted to explore the impact of various w/c ratios on the mechanical and shielding characteristics of heavyweight magnetite concrete. The parameters which were evaluated in this study are compressive and tensile strengths, modulus of elasticity, linear attenuation coefficient, mean free path, tenth value layer and half value layer. The Cs-137 and Co-60 radiation sources with different energy levels were applied. The obtained results indicated that mechanical and shielding characteristics and microstructure of heavyweight magnetite concrete improve with the reduction of w/c ratio. (C) 2019 Elsevier Ltd. All rights reserved.