A control device for a compression ignition engine is provided, which causes an injector to perform a pre-injection and a main injection, sets fuel injection timings of these injections so that an interval between a first peak of a heat release rate resulting from the combustion of fuel injected by the pre-injection and a second peak of the heat release rate resulting from the combustion of fuel injected by the main injection becomes an interval to make pressure waves caused by these combustions cancel each other out, and when an increase of an oxygen concentration of intake air supplied to a combustion chamber is detected, controls the injector to reduce the injection amount and retard the injection timing of the pre-injection compared with a case where the concentration increase is not detected under a condition that engine load and speed are the same.