Provided is a hybrid vehicle controller (20) that enables a hybrid vehicle (1) to smoothly achieve travel mode switching involving engine (2) start. The hybrid vehicle controller (20) includes a mode switching controller (25) configured to, in response to a predetermined mode switching request, perform mode switching control for switching from a first travel mode where an engine (2) is stopped and a drive wheel (8) is driven by drive power generated by an electric motor (3) to a second travel mode where the drive wheel (8) is driven by drive power generated by the engine (2) and drive power generated by the electric motor (3). The mode switching controller (25) includes a clutch controller (30), and the clutch controller (30) is configured to: upon receiving the mode switching request, bring a clutch (5) into a half-clutch state to start the engine (2) using rotation of a transmission shaft (4a); and upon determining that the engine (2) has started, shift the clutch (5) from the half-clutch state to a stand-by state and subsequently shift the clutch (5) to an engaged state, the stand-by state being a state which is intermediate between the half-clutch state and a disengaged state and in which the drive power of the engine (2) is not transmitted to the transmission shaft (4a).