Interleukin 11 (IL-11) is a multifunctional cytokine member of the IL-6 family. It is found in different organs and tissues and it is secreted by mesenchymal cells including fibroblasts, stromal cells, osteoclasts and epithelial cells. IL-11 receptor is an heterodimeric protein that is expressed by different hematopoietic lineages such as megakaryocyte, erythroid, and myeloid progenitors. In combination with other cytokines (IL-4, IL-3, and SCF), IL-11 regulates several hematopoiesis processes, including megakaryocyte maturation. IL-11 activates certain B and T cells and has a role in primary and secondary immune responses as modulator of auto-inflammation in favor of Th2 polarization and allergic reactions. In addition, IL-11 participates in the regulation of osteoclast differentiation and blastocyst implantation. IL-11 is under investigation for the treatment of osteoporosis, thrombocytopenia, and inflammatory conditions.