Background: Cubital tunnel syndrome is the second most common compressive neuropathy of the upper limb, and it is characterized by ulnar nerve compression at the elbow. Traditional surgical options, including simple decompression and anterior transposition, have limitations in addressing ulnar nerve instability. This study introduces and evaluates the short-term outcomes of a novel surgical technique, the fascio-aponeurotic epicondylar flap (FAEF), for stabilizing the ulnar nerve and managing its instability. Materials and methods: A retrospective study was conducted on ten patients with longstanding cubital tunnel syndrome and confirmed ulnar nerve dislocation or instability. All patients underwent surgical intervention using the FAEF technique, which involves creating a quadrangular fascial flap from the epicondylar fascia to stabilize the ulnar nerve within the retrocondylar groove. Outcomes were assessed using clinical follow-ups, the Michigan Hand Outcomes Questionnaire (MHQ), VAS, and qDASH scores over a 90-day postoperative period. Results: All ten patients experienced complete resolution of neurological symptoms, including paresthesia, pain, and nerve clicking, by the final follow-up. Postoperative recovery was uneventful, with no complications such as infections or hematomas. Grip strength and hand functionality were fully restored, with significant improvements in MHQ scores (mean: 94). Dynamic elbow mobilization initiated on the first postoperative day resulted in full recovery of elbow range of motion. No recurrence of ulnar nerve dislocation was observed. Discussion: The FAEF technique effectively stabilizes the ulnar nerve, alleviates symptoms, and restores function while minimizing risks associated with traditional procedures, such as nerve trauma and elbow instability. By preserving the anatomical integrity of the medial epicondyle and enhancing nerve mobility, this approach represents a less invasive alternative to anterior transposition and medial epicondylectomy. Conclusions: The FAEF technique is a viable and effective surgical option for managing ulnar nerve instability in cubital tunnel syndrome. It offers a less invasive solution with excellent short-term outcomes, making it a promising addition to the surgical armamentarium for this condition. Further studies are warranted to evaluate long-term efficacy and broader applicability.