Down’s syndrome patients are prone to cervical ligamentous laxity, the vast majority of which is at the C1/2 level. We describe the case of a 2-year-old girl with Down’s syndrome who was found to have cervical instability at the C2/3 level on screening cervical spine radiographs with 9 mm of anterolisthesis of C2 on C3. She was without clinically evident neurological deficit from this condition; however, T₂-weighted magnetic resonance imaging of her cervical spine revealed high intensity signal changes within the spinal cord at and above that level. She underwent posterior fusion that was complicated by poor tolerance of her Minerva-type cervical brace. She eventually developed a stable fusion with 5 mm of anterolisthesis at the C2/3 level. This is the only Down’s syndrome patient with instability at the C2/3 level that we have found reported. Our experience suggests that Down’s syndrome patients can have instability at C2/3 that can be successfully treated with posterior fusion.