Abstract Thin films of amorphous indium tin oxide were deposited by soft sputtering. The film was gradually annealed in air at temperatures from 110°C to 150°C. Its structural and electrical properties were monitored in order to get a better understanding of the annealing process. Firstly, carrier density decreases by oxygen intake. Crystallization speeds up at 150°C, with a 2.5 D growth of crystallites. The preferred orientations come from sputtering induced seeds. Then, the carrier density increases again due to tin activation. Meanwhile, the carrier mobility is more damaged by the low temperature annealing in air than by a standard annealing in a reducing atmosphere. Thus, tin oxide segregation is suspected at grain boundaries.