The sensor bearing unit provides a bearing having an inner ring and an outer ring centered on an axis, the inner ring mounted on a shaft, and an impulse ring provided with a target holder and with a target mounted on the target holder, the target holder being secured to the inner ring. The target holder includes anti-rotation features adapted to cooperate with complementary anti-rotation features of the shaft so as to prevent angular movement of the impulse ring relative to the shaft by abutment in circumferential direction.