Escherichia coli NusA, an essential component of the RNA polymerase elongation complex, is involved in transcriptional elongation, termination, anti-termination, cold shock and stress-induced mutagenesis. In this study, we demonstrated that NusA can self-assemble into oligomers under heat shock conditions and that this property is largely determined by the C-terminal domain. In parallel with the self-assembly process, NusA also acquires chaperone activity. Furthermore, NusA overexpression results in the enhanced heat shock resistance of host cells, which may be due to the chaperone activity of NusA. Our results suggest that E. coli NusA can act as a protector to prevent protein aggregation under heat stress conditions in vitro and in the NusA-overexpressing strain. We propose a new hypothesis that NusA could serve as a molecular chaperone in addition to its functions as a transcription factor. However, it remains to be further investigated whether NusA has the same function under normal physiological conditions.