The anisotropic optical and electro-optic properties of ferroelectric Ba 0.7 Sr 0.3 TiO 3 thin films, deposited on highly transparent single-crystal MgO ͑001͒, ͑011͒, and ͑111͒ substrates using pulsed laser deposition, were investigated. The experimental results show a strong correlation between optical, electro-optic properties, and the orientation of Ba 0.7 Sr 0.3 TiO 3 thin films. The linear electro-optic coefficient r c of the ͑001͒, ͑011͒, and ͑111͒-oriented Ba 0.7 Sr 0.3 TiO 3 thin films are 99.1, 15.7, and 87.8 pm/V, respectively. Such a correlation may be attributed to the orientation dependent distribution and magnitude of spontaneous polarization.