Pollution is one of the major threats with potential risks to humans, animals and plants, especially pollution with heavy metals, which are characterized by their significant ability to accumulate in environmental systems and induce toxicity to living organisms, even at low concentrations and quantities. This study was conducted on some calcareous soils selected from the province s of Babylon and Diwaniyah. Soil samples were collected from ten sites, five sites from each province , from a depth of 0-30 cm, to determine the concentration of cobalt in its chemical forms (available, bound to calcium carbonate, bound to organic matter and oxides, and residual) and total concentration, in addition to knowing the effect of different soil characteristics on these chemical forms. The results showed that there was a relatively wide range in the total cobalt concentration in the study sites (16.58 - 86.76 mg kg-1), and the percentages of the available chemical phase of the metal ranged from 0.44% - 6.88%, and in the form associated with carbonates from 19.30% - 34.54%, and in the form associated with organic matter and oxides from 28.82% - 55.94%, and in the form associated with the residual fraction from 3.46% - 51.44%. Because the metals in these fractions might dissolve depending on environmental conditions, notably pH values, higher mobility levels of accessible metal ions and those partly bonded to calcium carbonate may suggest environmental contamination and a risk of toxicity in soils.