We report a simple and selective solution method to prepare Molybdenum Disulfide (MoS2) thin films for functional thin film transistors (TFTs). The selective area solution-processed MoS2 grows on top and around the gold (Au) source and drain electrodes and in the channel area of the TFT. MoS2 thicknesses in the channel area are in the order of 11 nm. A mechanism for the selective growth is also proposed. The Au electrodes act not only as contact, but also as a catalytic surface for the hydrazine hydrate used in the reaction, which induces the selective growth of MoS2 on the Au surface and into the channel region. This one step process demonstrates functional TFTs with a carrier mobility of ~0.4 cm2 V−1 s−1.