The critical temperatures and pressures of eight n-diaminoalkanes NH2(CH2)(n)NH2 with n = 2, 3, 4, 6, 8, 9, 10, and 12 have been measured. The method of pulse heating of a wire probe immersed into the liquid under study has been used. Residence times are from (0.03 to 1) ms. The critical properties of diaminoalkanes have been estimated by the group-contribution methods by Joback and Reid, Constantinou and Gani, and Marrero and Gani. These properties have also been calculated using a method based on the assumption that the functions describing the dependence of the critical properties of homologous series on the number of mers in a molecule should be self-similar and provide the scaling behavior for long-chain molecules. The last method provides the best accuracy in calculating the critical properties of diaminoalkanes. For this method, the average absolute errors are equal to 0.4% for the critical temperature and about 2% for the critical pressure.