The anomalies of the second-, third-, and fourth-order elastic constants have been derived for barium titanate and related compounds for the phase transition from cubic to tetragonal and from the tetragonal to the orthorhombic phases. The equilibrium values of the three components of the order parameter and the strain variables in the two phases have been obtained from the stability conditions. The fluctuations in the order parameter in the two phases have been derived from the Landau–Khalatnikov equations. Expressions have been given for the shift in the zero point energy in the tetragonal and orthorhombic phases, and these are shown to be proportional to (T−Tc)2. The anomalies for all the second-order elastic constants have been derived for both phases, and relations among them have been reported. It is shown that the elastic anomalies suffer a discontinuity at the transition temperature for both the phases. Our expressions give the temperature variation of the third-order elastic and fourth-order elastic constants for the phase transition from the tetragonal to the orthorhombic phase.