The method of Magnetic Adaptive Testing (MAT) was applied for investigation of ductile cast iron samples having matrix and graphite structure. This method is typical by its low required magnetization of samples, because it is based on the measurement of minor magnetic hysteresis loops and calculates magnetic descriptors for characterization of the sample. Results of the non-destructive magnetic tests were compared with the results of destructive mechanical measurements of Brinell hardness and also with the results of non-destructive eddy current measurements. Linear, sensitive correlation with low scatter of values was found between the magnetic and the mechanical characteristics. If the parameters of MAT measurement are properly chosen, then they do not depend on temperature in the T = 20-180°C range, in contrast to the results of eddy current measurements. Based on these results, MAT is suggested as a highly promising non-destructive alternative of destructive tests for monitoring structural changes in cast iron and in other ferromagnetic objects.