An internal combustion engine controller is applied to an internal combustion engine incorporating a turbocharger. The engine includes an intake passage, a compressor arranged in the intake passage, a bypass passage connecting portions of the intake passage at upstream and downstream sides of the compressor. An air bypass valve adjusts a flowrate of intake air passing through the bypass passage. The internal combustion engine controller includes an acceleration determination unit and an ABV control unit. The acceleration determination unit is configured to detect an acceleration request sent to the internal combustion engine and determine whether or not the acceleration request is in an initial stage. The ABV control unit is configured to execute a temporary open/close control to open the air bypass valve for a specified period when determined by the acceleration determination unit that the acceleration request is in the initial stage.