Elastic deformations during phase transition in freestanding BaTiO3 thin films were investigated. BaTiO3 films were prepared by sol-gel technique or RF magnetron sputtering on silicon substrates, covered by randomly oriented 120 nm thick Al2O3. The as-deposited films were under tensile stress of 100-170 MPa and did not show neither pyroelectric nor piezoelectric properties. Partial substrate removal caused the freestanding films to expand laterally by 0.3-0.5% and corrugate. Dielectric constant of the freestanding films (620±10) was found to be significantly higher than that of the substrate supported films (110±20). The freestanding films showed detectable piezoelectric effect, which indicated that the lateral expansion was originated from the substrate-suppressed cubic-tetragonal phase transition.