Successful incubation affects the number of healthy chicks in all poultry species. This study examined the effect of eggshell thickness on the hatching rates of guinea fowl and pheasant eggs. In total, 964 guinea fowl and 1,728 pheasant eggs were used in the study. Eggshell thickness was measured directly with an ultrasound gauge. Thicknesses ranged between 0.27-0.47 mm in guinea fowl and 0.24-0.49 mm in pheasant eggs. Incubation periods were 28 days for guinea fowl and 25 days for pheasant eggs. At the end of the incubation period, unhatched eggs were broken to identify the causes of embryonic mortality. Eggs were classified as thin-, medium-and thick-shelled, and hatching rates were calculated as a function of eggshell thickness. Differences in hatching rates of guinea fowl and pheasant eggs with different shell thicknesses were not statistically significant (p>0.05).