We explored the factors associated with the stress signs among children during the COVID-19 pandemic in Japan. Although children showed increased stress signs, they also showed increased development of good behavioral traits during this period. Parenting styles were significantly correlated with the psychological and physical stresses experienced by children. While a punitive parenting style had significant correlations with increased psychological and physical stress, a warm and permissive parenting style had positive correlations with increased good behavioral traits and behaviors of children even during the pandemic. Social support enhanced mothers' self-esteem and positive perceptions among children. These findings provide us with important clues to support families, during the era of the COVID-19 pandemic.