In light of the rapid increase in the number of working mothers and dual-earner families, workplace flexibility—including the availability of flextime, the ability to work from home, and part-time employment—has become a crucial support for working parents with young children in balancing work and family responsibilities. Numerous studies suggest the benefits of workplace flexibility for individuals’ well-being and their work-family conflict; however, research on how workplace flexibility influences relationships between family members is scarce. Guided by the perspectives of boundary-spanning resources (Voydanoff, 2005), the current study examined the associations of three types of workplace flexibility (i.e., access to flextime, ability to work from home, and part-time employment) with couples’ relationship quality and parent-child interaction among working parents with young children. The study also investigated these associations in the context of gender, household structure, and household income.,The study used data from the Early Childhood Longitudinal Study-Birth Cohort (ECLS-B), a nationally representative study of children born in the United States in 2001. The sample consisted of children’s mothers (N=7,700) and resident fathers (N=3,800), who participated in the 24-month and 48-month surveys. Flextime was measured using a dichotomous indicator for availability of flextime at parents’ current jobs. The ability to work from home was measured using a binary indicator of whether parents had a formal arrangement to work from home. Parents who worked fewer than 35 hours per week were considered part-time workers. Measures of couples’ relationship quality consisted of three scales: relationship happiness and scales of positive partner interaction (e.g., calmly discussing something and laughing together) and negative interaction (e.g., arguing about house chores or leisure time). Parent-child interaction was measured by social-recreational interaction (e.g., reading books, telling stories, playing games, and taking children out for a walk) and basic care interaction (e.g., changing diapers, dressing the children, and preparing meals). To address omitted variable bias, the study sequentially used 1) a pooled Ordinary Least Square regression model with extensive controls for demographic and employment characteristics, 2) a lagged-dependent model that additionally controlled for prior outcomes, and 3) a fixed-effect model, separately, for mothers and resident fathers. The study conducted interaction analyses to test moderating associations by gender, household structure (dual-earner parents vs. single-earner parents and single parent households vs. two-parent households), and household income (low-income vs. mid- and high-income households). ,The study found that, among mothers, working from home was consistently associated with greater relationship quality for couples and more frequent social-recreational interactions with their children. These positive associations were particularly pronounced among low-income mothers. Mothers’ part-time employment was also associated with greater relationship happiness and more frequent parent-child interactions while part-time employment may not be beneficial for parent-child interaction among single mothers. Flextime for mothers was not associated with couples’ relationship happiness and parent-child interaction, though it was associated with more frequent positive interactions for couples. ,Among resident fathers, flextime was consistently associated with higher couples’ relationship quality for couples and this positive association was stronger for dual-earner fathers. Flextime was also positively associated with basic care interaction, particularly for low-income fathers. However, fathers’ ability to work from home was associated with an increase in negative interaction for couples and this was particularly stronger for low-income fathers. Fathers’ part-time employment was associated with more frequent parent-child interactions, while this positive effect was reduced for low-income fathers. ,The findings suggest that distinctive types of workplace flexibility influence family relationship outcomes for mothers and fathers in varying situations. Moreover, it may work differently across household structure, and household income. The implications of workplace flexibility for parents in the context of work-family policies and social work were discussed.