Abstract The objective of the article is to analyze results of indirect calibration of three microhardness testers. The calibration was carried out by four appraisers using three reference blocks. The results were evaluated according to standard STN EN ISO 6507-2:2005 and by uncertainty analysis, unpaired t-test, the Analysis of Variance (ANOVA) and Z-score. All calibrated testers do not satisfy the condition of resolution. Only 5 calibrations (13.9 %) meet the conditions of standard. According to Analysis of Variability (ANOVA), the influence of appraisers on the microhardness is significant, especially for “soft” reference block and for tester No. 1. Maximum number of statistically significant differences between mean microhardness, measured by one appraiser and specified microhardness of correspondent standard was obtained at calibration of tester No. 2 by t-test. Unsatisfactory or conditionally satisfactory values of z-score were observed at calibration of tester No. 3, but the values of testers No. 1 and 2 are satisfactory. The values of z-score measured by appraisers B and C at calibration of testers No. 1 and No. 2 exceeded the average. Using newer equipment with higher magnification (and with higher resolution) of the optical system and skilled appraisers for calibration is the way for improvement of the results of calibration.