(1) Background: Gradenigo's Syndrome (GS) is a rare complication of acute otitis media characterized by the triad of diplopia, otitis, and facial pain. The widespread use of antibiotics has significantly reduced its occurrence. (2) Case summary: We present the case of an elderly patient with T-cell lymphoma who developed neurological deficits resembling GS. The patient was ultimately diagnosed with invasive sinus aspergillosis. The diagnostic process was challenging due to the atypical clinical presentation and the lack of specific imaging findings. A biopsy was the most important test for clarifying the diagnosis. (3) Conclusions: The prognosis for this complication is extremely poor without surgery, and the patient died despite adequate antifungal coverage. Therefore, maintaining high clinical suspicion is paramount to avoid adverse outcomes in similar cases, particularly in the geriatric population, wherein this syndrome's occurrence may not be expected.