The effect of TiO₂ nanoparticle addition on mechanical properties of low carbon steel and the phases originated from this inoculation were investigated. Equilibrium phases were estimated by means of thermodynamic modeling and the results were compared with further microscopy characterization. Both techniques confirmed the dissolution of TiO₂ nanoparticles in the molten steel which derived in TiN and Ti₄C₂S₂ nanometric reaction products. The formation of these nanometric phases, were found to result in ferrite grain refinement and consequently in the enhancement of mechanical properties. In addition, the formation of these phases led to C and N depletion from the iron matrix and to a continuous yielding behavior in tensile stress–strain curves.