Spinal muscular atrophy (SMA) is a severe autosomal recessive disorder affecting one in every 10,000 live births. The disease is characterized by loss of alpha-motor neurons in the spinal cord that leads to progressive atrophy and weakness of limb and trunk muscles. This neuromuscular disorder results from deletions and/or mutations within the survival motor neuron 1 (SMN1) gene, leading to a pathologically decreased expression of functional full-length SMN protein. Here we report on the investigation to measure SMN protein levels through electrochemiluminescence immunoassay (ECLIA). This simple assay is a highly quantitative method able to measure SMN protein levels in human, mouse, and rat samples throughout a wide working range with low intra- and interassay error. The sensitivity for human SMN is 30 pg/mL and provides a new tool for the set up of high-throughput screening for basic research. Moreover, we describe a novel tool for a noninvasive assessment of SMN in buccal cells derived from healthy donors, SMA carriers, and SMA patients. The availability of a validated quantitative ECLIA should improve the investigation of novel compounds for the treatment of SMA.