The aim of this study was to determine the effect of egg water loss during storage and incubation on hatch rates in heavy-type broad-breasted white BUT Big 6 turkeys. Turkey hens started laying eggs at 30 weeks of age. In weeks 2, 8, 16 and 21 of the laying season, 1512 eggs were selected randomly and divided into 4 groups of 378 eggs each. The groups of eggs were stored for 7, 10, 13 or 17 days before incubation. At the beginning and end of the storage period and on days 9, 15, 21 and 24 of incubation, eggs were weighed to determine the percent water loss relative to the egg's weight. Four incubation cycles of 378 eggs each were performed for each storage period. A total of 16 incubation cycles were carried out (4 weeks of the laying season x 4 egg storage periods) and the following parameters were determined (%): egg fertilization, dead embryos, unhatched eggs and hatchability results from fertilized eggs. The percentages of dead embryos and unhatched poults with physical defects and abnormal position were determined in hatchery waste from each incubation cycle. Egg water loss varied throughout storage and reached 0.57% of total egg weight after 7 days, 0.79% after 10 days, 0.87% after 13 days and 1.28% after 17 days (P <= 0.05). After 7 days of storage, egg water loss during a 15-day and 21-day incubation period reached 5.76% and 8.72%, and lower values were noted after 17 days of storage (P <= 0.05). Egg water loss of 1.28% during storage resulted in a high rate of early embryonic mortality (14.81%) and a low hatch rate (72.12%) (P= 1% in weeks 16 and 21 of the laying season (P <= 0.05). Egg water loss during a 21-day incubation period was similar in weeks 2, 8 and 16 of the laying season, and lower in week 21 (P <= 0.05). The hatchability of turkey eggs was lowest in weeks 16 and 21 of the laying season (P <= 0.05). Low water loss during incubation contributed to a high rate of late embryonic mortality (13.2%). High water loss during egg storage is accompanied by lower water loss during incubation. Water loss should be monitored after storage and on days 15 and 21 of incubation to evaluate water metabolism in hatching eggs.