Background/Aims Early adverse life events (EALs) are relevant to irritable bowel syndrome in adulthood. Maternal separation (MS), as one of the EALs, has proved to induce visceral hypersensitivity in adult rats. However, the effect of MS on visceral hypersensitvity from the post-weaning period to adulthood remains unknown. Methods One hundred and ten neonatal Sprague-Dawley rats were randomly divided into 2 groups: rats in the MS group were exposed to 3 hours daily MS on postnatal day (PND) 2-14; the normal control (NC) group remained undisturbed. Visceral sensitivity was determined by measuring the visceromotor response to colorectal distention on PND21, 35, and 56. Anxiety-like behaviors were measured by the open field test. Results Compared with NC rats, MS rats showed significant visceral hypersensitivity from the post-weaning period to adult. The proportion of visceral hypersensitive rats decreased with age from 87.5% to 70.0% in the female MS group and from 90.0% to 66.7% in the male MS group. The relative VMR ratio of MS and NC on PND21 was higher than PND35 and PND56. MS rats showed decreased ability of movement and exploration to the novel environment in the post-weaning period, obesity in the prepubertal period, and more anxiety-like behaviors in adulthood. Conclusions MS can significantly affect visceral sensitivity and behaviors of rats in different age stages, especially in the post-weaning period. Visceral hypersensitivity of MS rats is more pronounced in the post-weaning period and slightly restored in adults. Thus, visceral hypersensitivity in the post-weaning period might play a more meaningful pathophysiologic role in the formation of adult irritable bowel syndrome.