Poly(oxymethylene) dimethyl ethers (OME) are attractive oxygenated fuel additives and physical solvents for the absorption of carbon dioxide. This works studies the synthesis of OME from formaldehyde and methanol in aqueous solutions. The reaction kinetics of OME formation is studied experimentally in a stirred batch reactor on a laboratory scale using the heterogeneous catalyst Amberlyst 46. The influences of the ratio of formaldehyde to methanol, the amount of water, and the temperature (303.15-363.15 K) are investigated. A model of the reaction kinetics is developed that differentiates two competing reaction mechanisms. The model explicitly accounts for the intermediates poly(oxymethylene) hemiformals and poly(oxymethylene) glycols.