Simultaneous quadriceps and patellar tendon rupture is rare. Mechanical factors and coexisting systemic and local factors are taken into consideration in the pathogenesis of these ruptures. In patients with some chronic systemic diseases, simultaneous rupture can occur spontaneously or with minor traumas. We present a case of simultaneous quadriceps and patellar tendon rupture in a 21-year-old man with chronic renal failure in this report. He was treated surgically by osseotendinous repair with suture anchors and supplemental cerclage wire fixation on both sides. He regained his normal knee joint functions 18 months after the operation.