The study examined the effect of stearin and paraffin adulteration of the wax foundation on brood survival. In combs formed on a stearin-adulterated wax foundation (10, 30, and 50% stearin, which means: 3.9, 11.7, and 19.5% of stearic acid, respectively), the survival of brood decreased statistically significantly (p ≤ 0.001) compared to the survival rates noted on a pure beeswax foundation. The brood appearance resembled the so-called scattered brood although the queens oviposited normally. The scattered brood was caused by the death of young larvae, most probably due to changes in the properties of royal jelly. Larvae transferred into stearin-adulterated wax cups died as well. The adulteration of the wax foundation with paraffin (10, 30, and 50%) did not reduce the survival of the brood but lowered the mechanical strength of the combs. Adulteration of wax with even a small amount of stearin/stearic acid makes it useless for apiculture.