A device and method for controlling an internal combustion engine having a catalytic converter. At least one actuating variable for the internal combustion engine is determined as a function of a system model of the catalytic converter and/or the internal combustion engine. The system model, a setpoint variable for the control and/or the actuating variable is adapted. Information about a modeled residual oxygen content in the exhaust gas downstream from the catalytic converter is determined using the system model. Information about an acquired residual oxygen content in the exhaust gas at the output of the catalytic converter is acquired. The information about the modeled residual oxygen content is compared with the information about the acquired residual oxygen content. A measure for an adaptation requirement is determined as a function of the result of the comparison.