The demographic composition in the United States has undergone shifts due to increasing immigration. This may change the way we think about families and children in the United States, and it is important to include immigrant families in parenting research. This study examined the relations between parent-child relationships and preschool-aged children's social-emotional functioning in the context of low-income families in the United States. We also explored how the relations between the two were moderated by parental nativity, specifically focusing on parents born in the United States and those who were born in Mexico and emigrated to the United States. The sample included 199 preschool children enrolled in Educare/Head Start programs and their parents, with 134 of the parents born in the United States and 65 born in Mexico. Parents reported parent-child closeness and conflict. Teachers reported children's social-emotional strengths and behavioral concerns. Assessors evaluated children's executive function and behavior regulation using structured tasks. The results showed that more parent-child conflict was related to more behavioral concerns and lower levels of executive function among children with U.S.-born parents but not among those with Mexico-born parents. The study suggests that the role of parenting in child social-emotional functioning may vary depending on cultural backgrounds among low-income families.