The kinetics and mechanism are reported for the oxidation of formaldehyde with air over a hydrophobic catalyst. The measured catalyst activity and selectivity varied with temperature. A mathematical model, based on the Mars-van Krevelen mechanism, has been developed which describes the determined catalyst selectivity and reaction rate. The advantage of using a hydrophobic catalyst over a conventional hydrophobic catalyst is demonstrated by the kinetic parameters. The model can also be used for the quantitative prediction of formaldehyde oxidation at various operating conditions.