Adiabatic calorimetric investigation of the low-temperature heat capacity of sodium tetrafluoroborate as well as a DSC study of the thermal behavior of potassium tetrafluoroborate and of lithium tetrafluoroborate and its hydrates were carried out. Temperatures and enthalpies of phase transitions at temperature above ambient were determined for potassium tetrafluoroborate, lithium tetrafluoroborate, and lithium tetrafluoroborate mono- and trihydrate. It was demonstrated that lithium tetrafluoroborate has only one phase transition in the solid at 300 K.