According to a method and apparatus for controlling the insertion process of a weft yarn, the weft yarn is temporarily exposed to a braking friction and the yarn tension is mechanically picked-up. In order to prevent the friction from having a disturbing or damaging effect on the yarn, the yarn tension is only temporarily picked-up during certain phases of the insertion process, in order to derive information from the tension curve that is useful for the control of the insertion process. In a power loom, in particular a jet, rapier or gripper shuttle loom, a tension sensor for sensing the tension of the weft yarn can be switched during insertion between its sensing position and a passive position in which it does not touch the weft yarn. Preferably, the tension sensor is integrated in the insertion brake or even forms the braking element itself.