The present invention provides novel, single chain Fc fusion proteins having improved properties. The invention provides single chain fusions of soluble proteins fused to the Fc region of an immunoglobulin via a novel linker comprising a constant region of an immunoglobulin light chain linked to a CH1 constant region of an immunoglobulin heavy chain. This novel linker confers favorable properties on the Fc fusion proteins of the invention such as improved bioactivity and increased half-life as compared to non-Fc fusion counterparts or as compared to prior art Fc fusion proteins. The novel Fc fusion protein scaffold as described herein may be designed to include soluble proteins of interest capable of binding or interacting with any target of interest. Preferably, the Fc fusion protein of the invention is a dimer. The dimer preferably forms via a disulfide bond between free cysteine residues in the hinge region of two monomeric Fc fusion proteins of the invention.