We sought to explore a possible association between higher parental socioeconomic position and lower child cancer mortality. We examined total cancer mortality as well as site-specific cancer mortality. We constructed a retrospective birth cohort by linking South Korean birth records to death records from 1995 to 2004. Parental socioeconomic position and birth characteristics were identified from the birth records. Parental education and occupation were examined as socioeconomic variables while sex, parental age, gestational age, birth weight, multiple birth, birth order, and the death of previous children were included as birth characteristics. Cancer deaths were identified from the death records. In total, 5711,337 births were analyzed, including 30,844,015 total person-years. The total number of deaths was 21,217, including 1102 children who died of cancer. Hazard ratios of cancer mortality according to parental socioeconomic position were calculated using a Cox proportional hazard analysis with adjustment for the birth characteristics. All socioeconomic measures except maternal occupation showed a significant inverse association with cancer mortality after adjusting for the birth characteristics. For paternal education, high school and middle school graduation or lower was associated with an increased hazard ratio of cancer mortality compared to university education or higher: 1.14 (1.00-1.29) and 1.29 (1.02-1.62), respectively. For maternal education, middle school graduation or lower was associated with a hazard ratio of 1.54 (1.21-1.95). For paternal occupation, manual work and economic inactivity were associated with increased hazard ratios as compared to non-manual work: 1.17 (1.02-1.34) and 1.34 (1.04-1.73), respectively. Inequalities were also found for leukemia and central nervous system tumors. The extent of the inequalities decreased after age 5, and only the 1-4-year-old group showed significant associations with parental socioeconomic position. We conclude that there is an inverse relationship between childhood cancer mortality and parental socioeconomic position in Korea.