Background: The purpose of the present study is to analyze the autonomic nervous activity in multiparas while resting, nursing, and rooming-in/rooming-out during days 1 to 3 of early postpartum period. Methods: Subjects were asked to record the actions they performed while wearing a heart rate monitor. Changes in autonomic nervous activity from 9 am to 12 pm and relaxation based on the relaxation (RE) scale were surveyed in multiparous women experiencing a normal postpartum period, on postpartum days 1 to 3. Results: Thirteen subjects were enrolled but heart rate data for all 3 days were available for only 5 of them. In these patients, the autonomic nervous activity (heat rate, high frequency [HF], or low frequency [LF]/HF) showed no significant differences between the days during any of the time periods. However, of the 3 days, day 2 demonstrated a lower HF and higher LF/HF. Subjective sense of relaxation was higher on postpartum day 3 compared to days 1 and 2, but there was no significant difference observed in the 3-day total score. Though no significant differences in HF and LF/HF at rest and during nursing were observed for any of the 3 days, there was a tendency for HF to be lower and LF/HF to be higher during nursing than at rest. Conclusions: Autonomic nervous activity demonstrated no significant major changes between the 3 days of postpartum (day 1 to 3). However, the lower HF and higher LF/HF during nursing and rooming-in suggest that even multiparas, who are supposedly accustomed to nursing and child-rearing, can be tense. Results suggest that multiparas require monitoring, personal care, and attention so that they can be relaxed and less tense while nursing and caring for their children.