Small heat shock proteins (Hsps) are one of most conserved molecular chaperones that protect stress-inducible denaturation of substrates in living organisms. Small Hsps consist of a large subfamily categorized by subcellular localization ranging in size from 12 to 40 kDa. Here, we identified and characterized a small Hsp 16.9 gene (EsHsp16.9) from Siberian wild rye (Elymus sibiricus L.). EsHsp16.9 is a 456-bp cDNA with an open reading frame predicted to encode a 151-amino acid protein. It possesses a conserved ɑ-crystallin domain, which is a unique domain for small Hsps; shares high sequence similarity with cytosolic class I small Hsps among the small Hsp subfamily in Arabidopsis; and is close (96% similarity) to small Hsp in wheat. Northern blot analysis showed that EsHsp16.9 transcripts were enhanced by heat, drought, arsenate, methyl viologen, and H2O2 treatments. Moreover, we expressed and purified recombinant EsHsp16.9 proteins in Escherichia coli to confirm its activity as a molecular chaperone. We found that recombinant EsHsp16.9 exhibits effective molecular chaperone activity, as determined by inhibition of thermal aggregation of malate dehydrogenase (MDH), which is broadly used as a model substrate.