Low birth weight (LBW) was confirmed as a risk of high blood pressure (BP) in later stages of life. Low-grade inflammation and deterioration of autonomic regulation play an important role in hypertension. However, the association between birth weight and hypertension are poorly understood. We examined this association in 33 healthy Japanese volunteers aged 18-23 years (14 men and 19 women), and investigated whether the relationship between LBW and hypertension risk factors differs between men and women. We measured the BP and heart rate variability (HRV) at rest and during postural change from a supine to a sitting position. Blood cell counts and levels of total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, triglyceride (TG), and high sensitivity C-reactive protein were measured. The Student’s t-test was performed to compare the means of two variables. The relationship between birth weight and indices of hypertension risk factors were analyzed using the Pearson correlation coefficient. One-way repeated-measures ANOVA and multiple comparison tests were performed to identify the influence of postural change. Men were taller (p < 0.001), weighed more (p < 0.01), had a higher resting BP (p < 0.05), and had higher TG levels (p < 0.05) and lower HDL-C levels (p < 0.001) compared to women. In men, high frequency components (HF), the index of parasympathetic nervous activities were lower in the LBW group compared to the normal birth weight (NBW) group (p < 0.05), and there was an inverse relationship between birth weight and HF in men as measured by HRV (r = 0.63, p < 0.05). After the postural change, systolic blood pressure (SBP), diastolic blood pressure, and heart rate (HR) showed no significant increases in men born with LBW, whereas men born with NBW had normal responses (p < 0.01). In women, the LBW individuals have blunted responses in HR and SBP compared to the NBW individuals. Similar to the results of earlier studies, healthy young men have lower HDL-C and higher TG levels compared to healthy young women in this study. Our results also show that healthy young men with a LBW have lower parasympathetic nervous activities compared to their counterparts with a NBW. In addition, among healthy young Japanese adults, both men and women with LBW may be less sensitive to postural changes in HR and BP. In conclusion, we suggest that, for both men and women, those born with LBW have higher risk of hypertension, in healthy young Japanese adults.