A control device for an internal combustion engine is provided. The internal combustion engine includes a cylinder, an in-cylinder pressure sensor, a fuel injection valve, and an alcohol concentration sensor. The control device includes an electronic control unit. The electronic control unit is configured to: carry out learning of fuel properties with the fuel injected from the fuel injection valve as a target; calculate a combustion speed parameter, showing a combustion speed, within the cylinder, of the fuel that is a learning target of the fuel properties, on a basis of the in-cylinder pressure; and determine that water is included in the fuel when the capacitance of the fuel detected by the alcohol concentration sensor is larger than a preset first threshold, and when the combustion speed of the fuel within the cylinder is smaller than a preset second threshold.