The authors report an exceptional case of an anterior horn syndrome associated with Sjögren's syndrome in a 58-year-old patient with a flaccid tetraparesis revealed by asymmetric atrophy and diffuse fasciculations associated with xerostomia and xerophthalmia. The electroneuromyography objectified a diffuse anterior horn syndrome. The brain MRI and spinal cord were normal. Laboratory tests revealed positive anti-SSA and anti-SSB antibody. The salivary glands biopsy objectified lymphocytic sialadenitis grade 3 of Chisholm. The Schirmer's test was abnormally low. Diagnosis of anterior horn syndrome as part of Sjögren's syndrome was retained. The methylprednisolone bolus allowed partial clinical improvement after 12 months of evolution. Therefore, in patients with isolated anterior horn involvement, a correct diagnosis of the underlying SS is often delayed or overlooked entirely; in these instances, standard clinicoserological assessment is recommendable.