A yarn brake for a two-for-one twisting spindle has a brake element mounted in the region of a hollow axle of the spindle between an upper and a lower brake face, the braking force being predeterminable in a defined manner by means of the pretensioning of at least one spring element, which acts on an axially displaceably mounted upper piston, in which the upper brake face is integrated, and the yarn brake being pneumatically releasable to introduce a yarn. The upper piston (27) receiving the upper brake face (28) is configured in such a way and guided with play (S) within a housing (16) of the yarn brake (14) in such a way that it can move aside if necessary into a position (I), in which its center longitudinal axis (37) forms an angle (α) with the center longitudinal axis (38) of the housing (16).