A method for feeding a yarn (F) under constant tension to a yarn processing point of a textile machine (T) distant from spool (2) or equivalent support from which the yarn (F) unwinds, the tension of said yarn (F) being controlled in proximity to the spool (2) such that this parameter is monitored and controlled immediately after the yarn (F) has been unwound from the spool (2), the yarn (F) fed to the textile machine (T) cooperating, before reaching said processing point on the machine (T), with a series of thread guide elements (8) which modify the tension of the regulated tension. A second tension control is effected in proximity to the textile machine (T), said control being used for further adjustment of the tension of the yarn (F) in proximity to the spool (2) to hence regulate the tension of the yarn (F) entering the machine (T) to a predetermined constant value.