Purpose <p>Sarcopenia involves age-related decline of muscle strength, mass, and physical capacity. Although age-related changes in speech are well recognized, their relationship with sarcopenia severity and underlying biological markers remains unclear.</p> Methods <p>Community-dwelling older men were classified as controls (<i>n</i> = 137) or as having probable (<i>n</i> = 122), definite (<i>n</i> = 94), or severe (<i>n</i> = 77) sarcopenia using standardized criteria. Acoustic voice measures, [maximum phonation time (MPT), harmonics-to-noise ratio (HNR), and cepstral peak prominence smoothed (CPPS)], were obtained using standardized protocols. Handgrip strength (HGS), muscle mass, short physical performance battery (SPPB), and plasma levels of C-terminal agrin fragment-22 (CAF22) and neurofilament light chain (NfL) were assessed.</p> Results <p>All voice measures declined progressively with increasing sarcopenia severity (<i>p</i> &lt; 0.05). Participants with definite and severe sarcopenia exhibited shorter MPT, lower HNR, and CPPS compared with controls. Voice biomarkers were positively associated with HGS and SPPB (<i>p</i> &lt; 0.05). Regression analysis demonstrated consistent independent inverse associations between voice biomarkers and higher CAF22 across sarcopenia categories, whereas associations with NfL were modest. Correlation analyses confirmed robust relationships between voice measures and CAF22 (r² = 0.113–0.181, all <i>p</i> &lt; 0.0001).</p> Conclusions <p>Speech-derived voice biomarkers explain sarcopenia severity and functional impairment in older adults and show strong biological associations with neuromuscular junction integrity.</p>