An isotopic investigation of organic matter of the Late Devonian-Carboniferous (Mississippian) conodont elements of various morphology was carried out. δ¹³C_org values of conodont elements measured in this study range from -32.6‰ to -22.4‰, with an average value of –26.1 ± 4.8‰. The study taxa represent four types of conodont apparatus, which differ one from another by morphology of P1 elements. In spite of apparently different morphology all the studied conodonts possess close δ¹³C_org values. Taxonomic control on the carbon isotope composition is insufficient as well. High consistency of the carbon isotope composition of conodont organic matter suggests that the Late Devonian and Carboniferous (Mississippian) conodonts occupied similar trophic levels. Quite low δ¹³C_org values in conodont organic matter allow supposing that conodonts were low level consumers, probably seston and plankton feeders.