A fixing device includes a flexible, tubular fixing rotator rotatable in a predetermined direction of rotation and an opposed rotator disposed opposite the fixing rotator. A nip formation pad presses against the opposed rotator via the fixing rotator to form a fixing nip between the fixing rotator and the opposed rotator, through which a recording medium bearing a toner image is conveyed. A fixing heater is disposed opposite at least a conveyance span of the fixing rotator in an axial direction thereof where the recording medium is conveyed to heat the fixing rotator. A lateral end heater is mounted on the nip formation pad and disposed opposite an inner circumferential surface of the fixing rotator at a lateral end of the fixing rotator in the axial direction thereof to heat the fixing rotator. A supplementary thermal conductor contacts the fixing rotator and the lateral end heater.