Improvement of quality as to iron ore pellets remains a relevant objective and meeting this challenge could significantly improve an efficiency of cast iron and HBI production. The purpose of this study lies in the assessment of potential to improve a strength of iron ore pellets by means of microstructure control. The results of the study showed that pellet compressive strength decreases monotonically at 20 daN/pellet per every 1% of porosity. The external signs of structure defects have been studied (e.g. small crack; large crack; pellet fragments; pellet aggregates). It was found out that most individual industrial-scale pellets have the optically detectable structure defects. Meanwhile, there is a lower content of fractured pellets and higher proportion of aggregates observed in the samples with high grade iron concentrate. The nature of the cracks also depends on the beneficiation degree of concentrates, i.e. the cracks tend to be predominantly concentric in the pellets with higher iron content, and the radial cracks appear mostly while the mass fraction of iron in the pellets is diminished. The control of microstructure parameters and pellet strength is feasible due to the following conditions: formation of the specified porosity by means of flux addition, application of polymer binders; minimization of incidence and height of green pellet overload; production of dense green pellets with min porosity; arrangement of pellet heat treatment with the constraints for defects to appear, namely: limitation of the drying and firing speed, ensuring max uniformity of the thermal field within width and height of pellet bed; limitation of cooling speed.