Postural change has frequently been used in clinical practice for pain relief, drainage, and prevention of pressure ulcers. In particular, 30° lateral position is known to be effective for body pressure dispersion, and is used in combination with body pressure dispersion mattresses. However, few studies have been conducted to estimate the effects of 30° lateral position and body pressure dispersion mattresses on circulation dynamics and autonomic nerve activity. A slight postural change may be associated with circulatory changes such as hypotension and bradycardia in critically ill patients and the elderly. The current study aimed to evaluate the effect of 30° lateral position on hemodynamics and autonomic nerve activity with three types of mattresses used in clinical practice. Eighteen healthy adult university student volunteers (8 males and 10 females) aged 18-22 years participated in the experiment. We measured blood pressure and heart rate (HR), analyzed heart rate variability based on electrocardiographic data, and evaluated autonomic nerve activity. The simultaneous measurement of body pressure distribution was performed on a standard mattress (Paracare KE-601Q) and two types of body pressure dispersion mattresses (Maxi KE-801A and Air MADV83A) using a sensor. These were analyzed before and after postural change using the paired t-test. p < 0.05 was considered significant. There were no significant differences in systolic blood pressure before and after postural change on any of the mattresses. In contrast, compared to the supine position, significant elevation of diastolic blood pressure was observed immediately following postural change (p = 0.02) and in the 30° lateral position (p = 0.02) on the Air mattress. HR was significantly lower in the 30° lateral position than in the supine position (Paracare: p = 0.002, Maxi: p = 0.01, Air: p = 0.001). HF, an index of parasympathetic nerve activity, was significantly increased in the 30° lateral position compared to immediately after postural change on the Maxi mattress (p = 0.003). However, no significant difference was found in LF/HF, an indicator of sympathetic nerve activity, between the supine and 30° lateral position on any of the mattresses. The sacral region was recorded as the maximum pressure point in the supine position, but this changed to the greater trochanter with a shift to the 30° lateral position. Our study indicates that postural change from a supine to 30° lateral position had little effect on autonomic nerve activity in healthy young adults. Although HR decreased slightly in the 30° lateral position, this did not have a major impact on autonomic nerve activity and the pressure applied to a point on the body.