The purpose of this study was to analyze the influence of the mothers’ nighttime responses on the sleep–wake rhythm of their 1-month-old infants. This study used an anonymous self-administered survey questionnaire with 1133 mothers of 1-month-old infants. The questionnaire investigated basic information about the parents, growth environment of infants, mothers’ sleep patterns during pregnancy, and infants’ sleep patterns at the age of one month. Logistic regression analysis was used to analyze the influence of nighttime responses on the risk of infants sleeping longer during the day than at night. Regarding nighttime response behavior, it was found that immediately picking up 1-month-old infants results in longer sleep during the day than at night (OR 1.616 [1.017 − 2.566], p = 0.042), compared to delaying picking up the infant. It was suggested that the stimulation due to picking up an infant may affect sleep–wake rhythm formation.