Phosphoinositol 3-kinase (PI3K) is critically important for the regulation of mast cells function. Through phosphoinositide-dependent kinase 1 (PDK1), PI3K activates the serum- and glucocorticoid-inducible kinase 3 (SGK3). The present study explored the role of SGK3 in mast cell function. Mast cells were isolated from bone marrow (BMMCs) of gene-targeted mice lacking SGK3 (sgk3^-/-) and their wild-type littermates (sgk3^+/+). Stimulation with IgE and cognate antigen triggered release of intracellular Ca²⁺ and extracellular Ca²⁺ entry. Influx of extracellular Ca²⁺ was significantly blunted in sgk3^-/- BMMCs as compared to sgk3^+/+ BMMCs. Antigen stimulation further led to a rapid increase of a K⁺-selective conductance in sgk3^+/+ BMMCs, an effect again blunted in sgk3^-/- BMMCs. ß-hexosaminidase release, triggered by antigen stimulation, was also decreased in sgk3^-/- BMMCs. IgE-dependent anaphylaxis measured as a sharp decrease of body temperature upon injection of DNP-HSA antigen was significantly blunted in sgk3^-/- as compared to sgk3^+/+ mice. In conclusion, both in vitro and in vivo functions of BMMCs are impaired in gene-targeted mice lacking SGK3. Thus, SGK3 is critically important for proper mast cell function.