Objective: This study investigated the effects of the firstborn’s gender and temperament on the fertility intention and follow-up childbirth of parents. Methods: A total 120 firstborns and their mothers were selected from the sample of the Panel Study on Korean Children. Child temperament traits were measured by Early Childhood Behavior Questionnaire(ECBQ) and mothers stated their fertility intention in 2009 when their first child was under 2 years old. Follow-up childbirth of mothers was assessed from the data of PSKC in 2016. Results: The results indicated that there was a significant difference by gender in follow-up birth. Among aspects of temperament, fertility intention was affected by the firstborn’s inhibitory control and follow-up birth was affected by the firstborn’s gender and discomfort. For mothers with a boy, the firstborn’s soothability affected mothers’ follow-up childbirth. Conclusion/Implications: These results imply that gender and temperament of the first child are connected to mothers’ fertility intention and follow-up childbirth. Extra studies are required to clarify how those factors affect mothers’ parenting or psychological status. Meanwhile, the firstborn’s gender and temperament should be considered when developing support programs for families with one child in order to increase follow-up birth rate.