Provided herein are formulations of PCSK9-binding polypeptides, such as those comprising evolocumab, that comprise N-acetyl arginine and have reduced viscosities when compared to formulations lacking N-acetyl arginine. Provided herein are also methods of formulating such compositions that are advantageous in that they conserve certain components. Such formulations comprising PCSK9-binding polypeptides can be administered to patients to treat and/or prevent PCSK9-related diseases, conditions, and disorders.