Modified relaxin polypeptides and their uses are provided. In one aspect, the disclosure provides a relaxin polypeptide comprising one or more non-naturally encoded amino acids. The polypeptide may be linked to a linker, polymer, or biologically active molecule. The serum half-life of the relaxin polypeptide may be enhanced relative to the unconjugated form. In another aspect, the disclosure provides methods of treating a patient having a disorder modulated by relaxin.