The heat capacity of yttrium aluminium garnet Y3Al5O12 (YAG) has been measured by low-temperature adiabatic calorimetry from 5 to 420 K. For temperatures up to 900 K the heat capacity has been derived from enthalpy-increment measurements (470-880K) using high-temperature drop calorimetry. The two sets of calorimetric data join smoothly and show no transition in the measured temperature range.