A non-invasive bodily-attached ambulatory medical monitoring and treatment device with pacing is provided. The noninvasive ambulatory pacing device includes a battery, at least one therapy electrode coupled to the battery, a memory storing information indicative of a patient's cardiac activity, and at least one processor coupled to the memory and the at least one therapy electrode. The at least one processor is configured to identify a cardiac arrhythmia within the information and execute at least one pacing routine to treat the identified cardiac arrhythmia.