The spectrum of proteins was studied in plerocercoids of parasitic cestodes Triaenophorus nodulosus collected from the liver of different species of fish: perch Perca fluviatilis L., ruffe Gymnocephalus cernuus L. and burbot Lota lota L. A comparison of protein extracts separated by 2D electrophoresis revealed 18 proteins whose concentrations differed among larvae of different fish species. Of these, 4 proteins were identified by using mass-spectrometric methods (MALDI-TOF/TOF, LC–MS): a carbohydrate metabolism enzyme triosephosphate isomerase, the proteins of microtubules tubulin α and β, and the G-protein signaling molecule. The elevated content of components of the G-protein pathway of the cytoskeleton and cell morphology regulation (tubulin and G-protein) in plerocercoids from perch in comparison with plerocercoids from burbot indicate a more dynamic cytoskeleton, increased cell proliferation and differentiation processes, and possibly more mature larvae in the former species. A higher level of expression of the key enzyme of glycolysis and signal transmission in plerocercoids from perch compared to plerocercoids from burbot indicates a greater metabolic activity in larvae from perch. The obtained results indicate that the expression of some proteins in T. nodulosus larvae is influenced by the habitat.