Abstract: A tennis net tightening assembly adapted for installation as a unit inside the upper end of an existing tennis net post and which comprises an elongated threaded shaft journaled between a pair of support plates, one of which contacts a portion of the lower inner wall surface of the net post while the other support plate is fitted to the lower portion of a collar which is adapted to seat on the top of the net post and extends upwardly therefrom. A captured nut is located on the threaded shaft and includes a hook for engaging one end of the net support cable. The support cable passes through a slot in the upper portion of the collar, which additionally includes a semi-circular cable guide element adjacent the slot. The elongated threaded shaft is journaled between the support plates and includes a shank at its upper end which passes through the collar and is protected thereby.