Undercorrected blepharoptosis can be encountered after frontalis sling operation. Revision surgery for undercorrection has commonly involved introducing a new sling material. We describe and evaluate a simple surgical technique to correct undercorrection by adjusting preexisting fascia. This is a retrospective interventional case series of patients undergoing sling revision between February 2010 and February 2017. Skin incision was made on the previous incision line. Careful dissection was performed superiorly to identify a preexisting fascia, and the dissected fascia was reattached to the tarsal plate using nonabsorbable sutures with adjustments for eyelid height and contour. The success of the procedure was defined as less than 1 mm of difference in the marginal reflex distance 1 of both eyes without any contour deformity. Twenty-one eyelids in 18 patients were included with a mean follow-up of 17.5 months (range 6-48) and a mean age of 14.7 years (range 5-57). All patients had undergone frontalis sling with autogenous fascia lata for congenital ptosis. Undercorrection due to recurrent ptosis was found in 12 eyelids, and contour deformity such as temporal ptosis was found in 9 eyelids. The mean time interval between previous frontalis sling operation and sling revision was 6.8 years. Nineteen patients (90.5%) achieved surgical success and a cosmetically acceptable appearance. Sling revision is a simple and effective method with low perioperative morbidity for cases of undercorrection or contour deformity following frontalis sling operation using autogenous fascia lata, even long after the primary procedure.