A model is presented to predict nonadiabatic combustion of syngas under gas turbine conditions. Mixing, combustion, and heat loss are described with four independent scalar variables. These are the mixture fraction, an enthalpy variable and two reaction progress variables for combustion of hydrogen and carbon monoxide. In the combustion model, turbulence is taken into account by weighting with an assumed shape probability density function. The model is used to calculate a 16-kW flame in an air cooled combustion chamber. The fuel consists of 40% CO, 40% H2, and 20% N2 resulting in a calorific value of 11.9 MJ/kg. The calculated CO, CO2, O2, and NO concentrations are compared with suction probe measurements at several locations in the combustion chamber. The nonadiabatic calculations and the measurements show good agreement. Adiabatic calculations show a significant overprediction of NO. It is concluded that the nonadiabatic model is necessary and suitable to calculate NO formation in flames with heat loss.