A belt retractor is provided which comprises a housing, a belt drum mounted in the housing so as to be rotatable about an axis of rotation, and a spring drive for the belt drum. The spring drive comprises an output drive part connected with the belt drum in such a manner as to prevent relative rotation, an intermediate part arranged rotatably in relation to the belt drum and to the housing and being centered on the axis of rotation of the belt drum, a wind-up spring effective between the housing and the intermediate part, an auxiliary spring effective between the intermediate part and the output drive part, and a spring cover. The spring cover and the output drive part are provided with receiving means coaxial to the belt drum and having interlocking means for a pin. The pin is simultaneously engageable with both of the receiving means in such a manner as to prevent relative rotation. The intermediate part is rotatably mounted on the pin. Furthermore, a method for mounting the spring drive of a belt retractor to the belt retractor is provide.