This disclosure relates to a thread control mechanism for sewing machines which will permit the machine operator to adjust the tightness of the stitch in accordance with the requirements of the particular work being sewn. The needle thread control mechanism includes a bracket plate which is conveniently mountable on a conventional sewing machine frame and which has mounted thereon an eyelet assembly for movement along a predetermined path and selected positioning thereof along such path so as to vary the extent of a thread loop which is formed between a thread tensioning device and the needle lever thread eyelet of the sewing machine, thereby controlling the tightness of the stitch being formed.