This study aimed to examine whether litters’ let-together system before weaning (‘kindergarten-system’) has any stress effect and effect on post-weaning behavior, respectively. One week before weaning piglets were socialized by removing four adjacent farrowing crate walls. After weaning, piglets from the same experimental groups were housed in the same rearing crates. The piglet’s body weight was measured at birth than weekly till the 7th life-week. Fecal cortisol metabolites were measured for evaluation of the adrenocortical activity. Personal observation and evaluation were carried out for behavioral analyses after weaning. There were no significant differences in weight development and cortisol metabolite levels between the control and experimental groups. Behavioral analysis showed that pigs grow up in a socialized system, rapidly evolve ranking in the rearing crates, and the self-maintenance and social behavior were more pronounced. In control groups, the activity involving movement (exploring, walking, and running) was much more decisive. Recent work suggested the beneficial effect of the ‘kindergarten’ system in the farrowing house in animal welfare aspects.