Calreticulin (CALR) is a multifunctional protein involved in molecular chaperoning and calcium homeostasis. CALR has also been associated with proliferation, cell cycle progression, migration, invasion and anoikis resistance in cancer cells. The prognostic impact of CALR expression is yet to be elucidated, however in some types of cancer, high CALR expression has been related to worse clinical outcomes. Notably, the discovery of recurrent mutations in the exon 9 of the CALR gene in myeloproliferative neoplasms has opened a new round of investigations. The present review contains data on CALR DNA/RNA, protein encoded and function.