The vibrational properties of barium strontium titanate thin films were studied by Raman spectroscopy in the temperature range from 5 to 300 K. The films were grown by pulsed laser deposition on SrTiO3 and LaAlO3 substrates with SrRuO3 buffer layers. Soft phonons are observed in Raman spectra of BaxSr1−xTiO3 films with Ba contents x = 0.05, 0.1, 0.2 and 0.5. The temperature dependence of the soft phonon frequencies and the splitting of the triply degenerated soft mode into two components of A and E symmetries indicate the ferroelectric phase transition. The E soft mode line is overdamped over a broad range of temperatures near the ferroelectric phase transition, while it is clearly seen in the spectra at temperatures away from the phase transition. The relative Raman intensity of the A soft mode and hard modes decreases gradually over a broad range of temperatures. This indicates a broad ferroelectric phase transition in the thin films. Comparison of Raman spectra for films grown on SrTiO3 and LaAlO3 substrates shows the influence of strain on the temperature of the ferroelectric phase transition.