In Brazil, the mining industry discards its tailing (IOT), commonly in dams, which pose risks to the local population and the environment. In addition, cement production is one of the main sources of carbon emissions during the manufacture of clinker. The IOT addition in cementitious materials prevents the construction of new tailings dams, and reduces the emission of carbon dioxide in the atmosphere as the need for clinker in Portland cement decreases. This paper aimed to evaluate the use of IOT as supplementary cementitious material and to investigate the impact of IOT chemical composition and content on the physical, mechanical and durability properties of cements blended with IOT. The accumulated heat of hydration, chemically modified water, remaining portlandite and calcium carbonate were reduced for IOT cements. Regarding the compressive strength, 10% IOT cements could be classified, according to the Brazilian standard, as CP-II-Z 40 while 20% IOT cements as CP-IV 32. There was a small increase of less than 1% for absorption of water and IOT improved the resistance to sulfuric acid in the cements. ANOVA verified that, statistically, the IOT chemical composition and content impacted all the results of the hardened cement blended with IOT. Hence, IOT as a partial replacement for clinker in Portland cement proved to be environmentally and commercially viable.