Abstract New structural and petrofabric data are presented from the Hombreiro pluton, a synkinematically emplaced granite located in the northern part of the Variscan belt of Spain. This pluton shows the imprint of two plastic deformations: the first is related to the motion of the Mondoñedo Nappe, with a top-to-the-east shear sense, and the later one to the Vivero Fault, an extensional shear zone with a top-to-the-west motion. These deformations initiated at high temperatures, close to the granite solidus as shown by the preservation of ⋎c⋎-slip fabrics in quartz. This fact indicates that extensional faulting was activated soon after the thrusting of the Mondoñedo Nappe during which the Hombreiro Granite was emplaced. We propose that the position of the Vivero Fault was controlled by a crustal instability induced by the intrusion of a number of plutons that delineate the footwall block of this fault.