Polyelectrolytes are a prospective tool for protection of proteins against aggregation. We compared synthetic polyanion, poly(styrene sulfonate), and natural chaperones of different types, namely, GroEL-like chaperonin from Pseudomonas aeruginosa phage EL and human small heat shock protein HspB5 (αB-crystallin), in their ability to prevent aggregation of client proteins. At 45 °C, all three agents efficiently suppressed thermal aggregation of phage endolysin. At higher temperatures, HspB5 and poly(styrene sulfonate) also inhibited endolysin aggregation, though polyanion became less efficient than HspB5 at 55 °C and 60 °C. However, the polyanion completely protected another protein, glyceraldehyde-3-phosphate dehydrogenase, even at 60 °C, in contrast to both natural chaperones whose effect disappeared at 50–55 °C. These results provide a platform for the development of artificial chaperones based on synthetic polyelectrolytes.