A mode transition control device is provided for a hybrid vehicle. The mode transition control device reduces a sensation of discomfort that may be imparted to a driver at a time of a mode transition from a series traveling mode to a parallel traveling mode during traveling. During mode transition from the series traveling mode to the parallel traveling mode in a hybrid vehicle, a gear shift stage is selected such that a rotational speed change amount of an internal combustion engine accompanying mode transition is less than or equal to a predetermined threshold value.