Objectives To determine the relation of paternal lifelong socioeconomic position (SEP) to the racial disparity in low birth weight (<2500 g, LBW) rates. Methods Stratified and multilevel logistic regression analyses were performed on an Illinois transgenerational dataset of infants (1989-1991) and their parents (1956-1976) with appended U.S. census income data. The neighborhood incomes of father's place of residence at the time of his birth and at the time of his infant's birth were used to measure of lifelong SEP. Population attributable risk (PAR) percentages were calculated to estimate the percentage of LBW infants attributable to paternal low SEP. Results In Cook County, infants (n = 10,168) born to fathers with a lifelong high SEP had a LBW rate of 3.7 %. LBW rates rose among infants born to fathers with early-life (n = 7224), adulthood (n = 2913), or lifelong (n = 7288) low SEP: 5.2, 6.9, and 9.3 %, respectively. The adjusted (controlling for maternal demographic characteristics) OR of LBW for fathers with an early-life, adulthood, or lifelong low (compared to lifelong high) SEP equaled 1.4 (1.2, 1.6), 1.5 (1.3, 1.9), and 2.0 (1.7, 2.3), respectively. The PAR percentages of LBW for paternal low SEP were 40 and 9 % among African-American and White mothers, respectively. Among fathers with a lifelong high SEP, the adjusted OR of LBW for African-American (compared to White) mothers was 1.1 (0.7, 1.7). Conclusions Low paternal SEP is a novel risk factor for infant LBW independent of maternal demographic characteristics. This phenomenon is particularly relevant to the African-American women's birth outcome disadvantage.