Abstract The garnet-type Li6La3ZrTaO12 (LLZT) solid electrolyte films were fabricated by aerosol deposition (AD) method. Ball-milled LLZT powder with a cubic garnet structure and a particle size of 1–2 µm was used as raw material and deposited directly on a SUS316L or a glass substrate via impact consolidation. As-deposited LLZT film has a cubic garnet structure but contains Li2CO3 and La2Zr2O7 phases. SEM observation revealed that the film consists of LLZT particles fractured into submicron size. The impurity phase formation during AD process was caused by the local heating by the collision between LLZT particles and deposition surface and reaction with CO2. The Li+ ion conductivity of LLZT film was estimated to be 0.24 × 10−5 S cm−1 at room temperature. Electronic conductivity of LLZT film was confirmed to be around 10–12 S cm−1, indicating the dominant Li+ ion conduction of LLZT film.