Systems and methods for assessing sympathetic nervous system (SNS) tone for renal neuromodulation therapy are disclosed herein. A system configured in accordance with embodiments of the present technology can include, for example, a detector attached to or implanted in a patient and a receiver communicatively coupled to the detector. The detector can measure cardiac data and the receiver and/or a device communicatively coupled thereto can analyze the cardiac data to provide one or more SNS tone indicators. The SNS tone indicators can be used to determine whether a patient will be responsive to a neuromodulation therapy and/or whether a neuromodulation therapy was effective.