The purpose of this study was to examine the relationships between parents' control, affectionate parenting behavior, preschooler's effortful control, prosocial behavior, and cognitive problem-solving ability. The subjects for this study comprised 221 preschoolers (104 boys, 117 girls) and their parents. The major results of this study were as follows. First, parents' effortful control revealed direct effects upon preschooler's effortful control, and affectionate parenting behavior mediated the effects of parents' effortful control upon preschooler's effortful control. Second, preschooler's effortful control mediated the effects of affectionate parenting behavior upon preschooler's prosocial behavior. Third, preschooler's effortful control had direct effects upon prosocial behavior, and prosocial behavior mediated the effects of preschooler's effortful control upon cognitive problem-solving ability. In conclusion, parents' effortful control and affectionate parenting behavior impacted upon preschooler's effortful control. And preschooler’s effortful control had an important role upon prosocial behavior and cognitive problem-solving ability.