Background: Injury to the quadriceps tendon is rare and most commonly occurs in middle-aged men. Few reports are available regarding outcomes after quadriceps tendon rupture in younger patients. Purpose/Hypothesis: To review the clinical outcomes of patients who underwent quadriceps tendon repair at age ≤40 years. We hypothesized that this cohort would experience better clinical outcomes in comparison to historical older controls. Study Design: Case series; Level of evidence, 4. Methods: Using an institutional database, we retrospectively identified patients who underwent quadriceps tendon repair between January 2009 and December 2017. Patients were included in the study if they were aged ≤40 years at the time of surgery and had sustained an isolated, complete tendon rupture. Patient and injury characteristics were recorded. Patients were contacted to complete a custom survey, the 2000 International Knee Documentation Committee (IKDC) form, the Lysholm scale, and the Tegner scale. Results: Included were 38 patients (86.8% male; mean age, 32.0 ± 6.9 years; age range, 15-40 years), with a mean follow-up of 5.9 ± 2.3 years (range, 2.4-11.3 years). At final follow-up, the mean IKDC score was 74.1 ± 22.6 (range, 26.4-100.0), and the mean Lysholm score was 85.4 ± 20.0 (range, 30-100), which were similar if not inferior to historical controls of patients >40 years. Only 16 patients (42.1%) had unchanged or higher Tegner scores after surgery, whereas 22 patients (57.9%) reported lower postoperative activity level. Overall, 91.2% (31/34) of workers returned at a mean 3.9 months after surgery, whereas 63% (12/19) of athletes were able to return to play at 8.8 months. At final follow-up, 12 patients (31.6%) reported persistent pain and stiffness in their knees. Additionally, 3 patients (7.9%) reported pain without stiffness, and 4 (10.5%) reported stiffness without pain. Patients reporting pain or stiffness had significantly lower IKDC scores, Lysholm scores, postoperative Tegner scores, and change in their Tegner score at final follow-up in comparison to those who did not report pain or stiffness. Conclusion: Although patients aged ≤40 years had satisfactory outcomes after quadriceps tendon repair, this injury resulted in significant long-term sequelae in a substantial percentage of patients, despite their youth. Further, this group did not have better outcomes compared with historical controls aged > 40 years.